Both are great. Ft Lauderdale has a bunch of gay b&b's with clothing optional pools and good clubs in Wilton Manors. You'll drive to get around but there are superb beaches and if you like, a nude gay beach called Haulover (the northern 1/3 is the gay end). You can also easily drive down to Miami or SouthBeach and there are restaurants of every kind easily gotten to. Key West is more crazy but also has gay b&b's, some clothing optional and a few gay clubs but mainly you just wander around, enjoy the crazy atmosphere and interesting architecture. You'll definitely feel like you've been away in Key West but no beaches and no need for a car though the drive down the Keys is beautiful though long.
Pretty accurate. The first half of the trip down the Keys, and getting there, is kinda unappealing these days, in my view. From the middle Keys onward (and you're actually mostly driving west by southwest at that point) it gets more attractive. Driving to Key West is about 100 miles after you leave Homestead and Florida City on the mainland.
There are really only 3 gay & clothing optional guesthouses (not technically B&Bs) remaining in KW. Island House, the Equator, and New Orleans House. I can discuss the pros & cons of each with you, I've stayed at them all.
KW does have public beaches, but just strips of sand on the Atlantic side. And a few private beaches at the newer mega hotels that have gone up. The water is remarkably shallow until quite far out in most spots, and very placid, but it also seems to be the reason the water's exceptionally warm, especially in August.
Back up slightly north of Miami Beach is Haulover, a legal clothing optional beach, created by public referendum. Wear a suit if you want, I like its less developed nature. But still with lifeguards, showers, comfort stations, and daily beach raking. The north end is informally the gay section, the middle the lesbian, the southern end mostly straight. Further south is a conventional clothed beach.