Well, the one gay bar I was in was decorated a little nicer than any other bar I've ever been in, but maybe that's not saying much considering I haven't been in many regular bars, either. The gay bar I was in was also a lot quieter than any other bar I've been in, nearly dead silent, actually. The bar I was in was actually technically a lesbian bar, but it was a guys' night the night I was there. There is music, but it's a lot more subdued and the bar I was in had a big screen TV tuned to CNN. This was in 2011, mind you and a lot's changed since then. I don't remember much else about the time I spent in that bar considering how long ago it was and it was only the one time. But yeah, I think it depends on the gay bar. I know the OTHER gay bar in my area can get kind of rowdy, so there's that. Basically a gay bar is just a bar but a little bit nicer than your typical bar.
It depends on the bar. My town has two and one of them has drag or burlesque shows several nights a week, but otherwise you wouldn't know it's a gay bar. The other one has loads of phallic art and jokes and things. lol. Both here seem like they're more places to meet existing friends than to make new ones, but I'm not sure if that's typical.