All earlier 535s don't necessarily have thin necks. First, since they were all hand carved, there was some variation in the necks. They had templates to check as they were working the neck, but they would vary. My 535 neck (2005) is rounder and beefier than my 03 H157 or 87 H-140. There's a slight difference in shape as well. Second, different people did the carving. Marv could be different from Arnie.
The guitars from the past few years have tended to be on the thicker side, but you'll still see a bit of variation between individual instruments.
If you have the opportunity to play the guitar first, I would highly advise that. Some people are very picky about the feel, others can play varying thicknesses, but shape makes a difference. My Strat has a VERY thick neck, my 140 is relatively thin. Both are comfortable. I've played several PRS guitars and I hated the shape. They hit my thumb in a manner that was actually painful in a short time. I have a dislike of wide/flat necks.
Hardware can be changed if you want, but the neck and body are pretty much set in stone.... er... wood.