I was wondering if, instead of putting a normal concrete material on a tile mesh, I put a PBR texture (the image sizes are 2k) on a tile mesh with SurfaceAppearance.
Would the PBR material on the tile mesh be more laggier than the normal concrete material on the tile mesh?
Well that probably might cause lag because your not using a normal material but try it to see if it does 
Usually custom materials are a bit more laggy.
I am using PBR textures with SurfaceAppearence to make a showcase game. Not my models or textures, free-models. Although I don’t think it’s any more lag inducing. In-fact it probably is less lag inducing than using a texture. Go crazy and have fun, good luck!
If you use a lot of textures, yes your game will probably take longer to load and be laggier.