It goes without saying / makes common sense that independent motion is superior for symmetry. Dumbbells allow a full range of motion, and, unlike machines, don't limit the motion through a particular axis, so they involve more stabilizers and assistors. With a full range of motion, also, comes a full stretch. A stretched muscle can be up to 30% larger than a non-stretched muscle.
Esoteric stuff really isn't necessary and increases chance of injury. A full range of motion, under control, at the proper cadence, is what works best. 1/2 reps, partial reps, really aren't a good idea. Because you can lift more in the eccentric part of any particular movement, occasional negatives can be o.k. for a seasoned lifter, but, probably aren't a good idea for a novice. Stretching (isometrics) is essential for injury prevention and full muscle development, but doesn't increase contractile proteins. There's a number of schools of thought about how to strengthen tendons, and ligaments, and you'll have to choose which you wish to believe.
Strength and size, are fairly independent of each other. You'll want to study muscular hypertrophy to understand this more fully.
To fully understand this, you need to research sarcoplasmic hypertrophy. It might well be something quite different than what you think it is.