my cats (rest in peace) would always "hang out" at the back of the tank. They rarely came to the front. They didn't seem to stay at the mid-bottom as previously stated, but rather would hide behind anything at any level. They're great to look at, but are shy, and don't really do much of anything.
Also, they like to hide, and sit motionless, and are see-thru, so therefore they are difficult to find sometimes, especially if you have plants...
As for compatibility, they stick together, so I am not sure any other community fish would bother them at all...I had them with skirt tetras, GBRs, madagascar/boesemani rainbows, and core cats, and the glass cats didn't care at all.
75g FW Planted Community; 55g African Cichlid
29g Biocube SW Reef;12g AP Mantis Shrimp/Brittle Star
2 Cats, 2 Dogs, 5 Turtles