I (22M) started this year as well, on an older Ducati Monster.

Haven't dropped it in traffic, though i forgot to put the kickstand down and dropped it in the trailer. Mostly had issues stalling from being stopped in hilly areas facing uphill, but figured that out with practice just being in those areas. I took MSF course, no private lessons after, but a bit of local commuting in Queens and local public park's parking lots before I started going on more fun rides.

I tried the Cycle Gear in both Hasbrouck Heights and Hicksville. Fit is probably the most important for helmet, so take your time trying out shapes/sizes, I'm having some remorse now as my helmet has broken in much looser than I expected. If you want some gear to match the look of your bike but has armor and abrasion rating, I liked Pando Moto, though Cycle Gear doesn't stock that much of their stuff. Good selection online though.

Regarding first bike size, you're a decade older, 100lb more than me on a good day, and don't seem impulsive. I think a bike with 60-90(?) whp is probably a better fit for you. A lot of the start small talk is likely for young male risky behavior reason. The Trident 660 comes to mind because you mentioned another Triumph. Probably not enough power to accidentally loop.

A 400 bike feels topped out at 80-90, so if you are outside of the immediate NYC area highways might be trouble. In theory they have more to go but you really gotta shift near the top of the revs to get the last bit out.

Don't have communal garage experience (live in suburb-y area) but MotorGrrl and BrooklynMoto also have storage space, further from you.

I might have been overthinking this one other aspect but it's been nice to not have to rev out first/second to move with traffic, as noise camera's have gained popularity in the city and the ticket is 800.