Yeah you can shop at any of the stores with any of the characters. Like even Trevor who wouldn't normally wear nice clothes from ponsybys can still shop there and buy nice suits.
I am also pleasantly surprised by the clothing options, one of my big complaints about 4 was that there was barely any different kinds of clothes (only 2 hats and 2 glasses in the whole game), especially after San Andreas had a crapload of clothes to pick from.
And to answer your question earlier, yes, you can do golf with Trevor as well. I was playing golf against trevor as Michael, and I thought it was pretty cool how Trevor svcked at golf and always freaks out when he misses a shot, what you think trevor would be like with golf. playing against franklin was a bit more of a challenge, as he wasn't as bad as trevor. I haven't played against Michael yet, but I assume out of the three that he would be the one who is good at it.
Hunting with trevor is also pretty fun too.