Got your email. Umm. What do I think? I think you have potential. Understand, these things take months, and years, to accomplish, and, some of us are better suited at it than others. When I was 17, I knew nothing about nutrition, nor training method, nor performance enhancement, and I still ended up 5'th in my high school for strength index, and 175# at 5'5", and 12%. For some guys, like me, it's much easier. I look at weights and get bigger. When I was 28, I was 230 at 12%. Now,...I'm old, and despite doing everything right, every year, the numbers slide just a bit.
Here's the reality of things. You almost certainly won't look like a guy on a cover of a magazine. For most, that look isn't attainable, and for those who do, it's hard work to keep it for any period of time. That "look" requires doing everything...eating perfectly, having great genes, years training, great diet, hours of HIIT and cardio, and..to be in the mag, a whole other handful of tricks that most folks don't, can't, or shouldn't, do. It's work, and it requires the strictest of discipline for most folks. A 24 hour a day thing if you will.
For most folks, there's a happy medium. In your case, just by looking at your pictures, I can see you have lots of potential. I'd be better able to see that if you were facing the camera in such a way as to show your "lines" and bone structure, but, it's clear you're not ectomorphic.
You're just becoming a man. Getting mature muscle takes time. You need to eat, and continue to lift. 5'8" and 170" isn't starving, and it's not underweight. If you wanna' be "stocky", eat more. If you wanna' be lean, you have to do HIIT, and cardio, and watch your insulin levels by eating moderate to low glycemic index carbs, and eating enough to sustain high activity levels and yet fall just short of a caloric overage. The trick in getting lean is keeping your metabolism up. That isn't accomplished by caloric restriction. Caloric restriction teaches your body how to be a fat-storing machine, and that's not what you want. You want a stoked furnace. You do that with calories, and intense activity. Small meals often, with adequate, but not to much carbs. Here's the trick, everyone's body works in a bit different from the next guy. For one person, 6000 calories might be right. For another person, 4000 calories might not be enough.
I got big by eating hard, training consistently, having genes, and working my behind off, but it's also what I have a passion for; what I've been doing for 34 years; what my genetic inclination is. For a show, I'll do three-a-days for 18 weeks. In 2007, I went 23 weeks without about four pieces of bread. I'd do HIIT in the morning. I'd workout in the afternoon. I'd do HIIT at night. I'd walk the shore line right before going to bed. Most folks aren't willing, or aren't able, to make that level of commitment. It's work. For me, I love the transformation I can effect, and I love the feel of being very fit and strong. It's a very primal thing...attraction..appearance..fitness..sexuality. Anyway...for you, watch the fast carbs, small meals often, do HIIT (stairs for 12 minutes works for me), stay consistent in your workouts, allow yourself to eat, and don't fret about being fat...you're 20 years old..enjoy it. As your body spends more time in the presence of testosterone, your muscles will mature (you'll "fill out"...I think for you that'll be easy, as long as you don't starve yourself). If you eat, train consistently, even slam a few beers and some pizza, you'll gain.
Understand, to get bigger, you need calories. Sacriplasmic hypertrophy isn't about strength. It's more about getting "pumped up." Lots of guys don't understand that. You need to keep your reps higher (say, 6 to 20 on upper body, and 8 to 25 on lower) if you want size. To get leaner, you need to get busy, and do it with enough calories to prevent the lag. That is the tricky part. Perfect form is essential.
Here's a simple maintenance equation that goes way back. Some will say it's off but, it's served me well. For each pound of lean muscle mass, multiple by 20, if you're less than 25; over 25 multiply by 15. So, a 180% guy with 12% fat would have 21.6 pounds of fat. That leaves 158.4 LBM. 20 * 158.4 = 3168. Now, add 600 for working out. Add 600 for HIIT or cardio. Subtract 600 for weight loss / leaning out. As you can see, 2300, is about 1000 short...just for maintaining. Protein is important, but, carbs are fuel and are protein sparing, and provide the ability to do more work, and you need your good fats (poly and mono). Stay away from fried foods, and refined sugars because fried foods are icky for you, and fast sugars, will drive your insulin way up, which will make it a lot harder to stay lean. Now, to stay full...DO do some fast sugar in the golden hour post workout.
You have to experiment with works best for you.
Some of those guys in the mags, have been juiced since they were 15 years old. Some have incredible genes. Some started when they were 12 years old. I have one friend, who is now a pro, who has juiced since he was 15. He's freaky big, but, almost too much so. He's spent a lot of money, and a lot of time, getting there. Thing is he's basically a gigolo for a living. In my view, it's not worth that, but, it's what he has always wanted. My buddy also has done extensive pump and pose (injected the fascia full of oil to get huge), lives on a boatload of androgen, takes EPO, takes diuretic, takes T3, takes GH, burns through nutrition supplements, and is really, even at 5'8" and 250#, an insecure jerk. My point being that the guys in the mag are a chemical masterpiece, along with lots of hard work, and years of training. That's what sells, but, it's not what most folks can accomplish and for those that do it's not without some cost in money, time, labor, health. For some, though, it's their passion, and their reward. It's all in what you want.
So...it gets down to what I say, here, over, and over, and over. Eat, lift, do HIIT, sleep; make sure you eat enough to support your activity, and eat just a teeny bit less if you wanna' get lean. Don't starve. Be consistent in staying active; don't be afraid to take a day off, though; do shit you love doing; keep at it; make realistic goals (you're not going look like the guy who's all juiced up and dried out), and have fun with it. Don't get into getting fat (bulking) and cutting (starving). Stay close to the look you want all the the time, but, just eat a bit less, or more, depending which direction you want to go. Enjoy the way it all FEELS.
Bodybuilding, at its heart, and in competition, is a cosmetic endeavor. You can't confuse it with just general fitness, although, excellent fitness is required. How do you think a guy has 24 inch arms? I'll tell you. Pump and Pose. Like any sport, there's certain things that the folks at the top of the game do, whether it's the broken bones of motocross, the imbalanced body of swimming, the endless hours of biking. For most, more reasonable goals are prudent. Sports performance is done with technology and the science of manipulation. A guy on a stage understands that science and uses it to affect a certain look. Other sports apply technology (from swimsuits to skis to skates to sleds to bikes to a wide variety of peaking methods) in various ways. High level is almost always about better science, in addition to great genes, coaching, and work ethic.
For most, it's fun to be hunky and feel good. Don't sweat the small stuff. You're a good looking kid, well on your way to being hunky.
The answer about bulking or cutting. Neither. Do what makes you happy.