I’m a beginner and am looking for a good optimization for my Android game, which is with lag, so I wanted some tips to make everything smoother, the scenario is a small town I made using UCP assets, so I thought I could combine all the Streets, houses, and buildings in only one or two geometries, is that a good idea?
It depends on what is visible in the scene at once. If you can see the whole town, then yes, combining will reduce the # of draw calls. Turn on Stats (the drop-down in the Game View.) From there you can see # of draw calls, batches, etc. If you have the Profiler in your version of Unity, use it as well to see where you are spending game cycles.
Using a single texture atlas will help a ton as well if you can get away with it. You want to have combined geometry + combined textures.
This is all true. Moreover, I’d suggest checking the number of lights in your scene, bake them as much as possible, and, in case you’re using some type of collider, try to stick with BoxColliders as much as possible.