There's a tourist office in Mestia (It's semi-touristy), which supplied some semi-decent maps (to purchase) there are lots of trails around. My husband also had access to old soviet era maps, but I don't know how it got them unfortunately. The hiking itself I remember the paths are not that well maintained, but the more popular ones are well marked, I don't recall us getting lost. Unless you are going in July be prepared for snow. Fantastic views of the Caucases around there and the hikes bring you past glaciers, some of the most breathtaking hiking I have done, we wild camped along the way and foraged raspberries to supplement our food. Most of the hikes are multi-day, so you will have to be self sufficient.
Never drove there unfortunately, we took a bus and train. I remember the taxi drivers being quite insane so they are not sensible drivers as you would expect from that part of the world, but once you reach that part of the counrty where Mestia are the roads become dirt tracks beyond and we felt safe enough to cycle mountain bikes on them (you can hire them in Mestia) to reach the trail heads.
Sorry I can't be much more help it's been a while since I went.
very happy with cheese and eggs etc