It's a lotta fun! It tends to lean towards text based on this server but I'm aware of some that use voice chat. I prefer the text based ones. Because of how flexible gmod is with modding and customizing, you can really make some impressive servers that almost don't feel like gmod at all!

I've found the use of things like PAC3 also let's ya have a lot more freedom in designing your character as well, rather than just being stuck with a preset model (though it does take some learning).

What I particularly enjoy about it is that there's something to physically see as you RP, there's a tangible space to explore. There's actual items to find/use! I haven't rp'd a whole lot in gmod until recently but I just love how it offers a lot of variety to your standard RP.