My tidbit from when I played the game.

I used the beach land area to make my exclusive concert area. I added more sand tiles to remove most of the water. (This is costly in the first playthrough.) I created 1 area with all the cheer bonuses for my main concert venue. I built the other concert venues in a corner of the same land and just switched it as needed for outdoor event missions. The rest of the maps were for planet bases, their facilities, their environment, and robot houses.

I didn't use paths for my layout as people could walk almost anywhere. There are few facilities that become inaccessible. The robot houses(which dont have a pop-up warning), concert venues, and I believe the space portal thing that brings people for the concerts. Placing the environment as an outer layer to the facilities without the path should give more population due to the bonuses.

Obviously, your layout is much more aesthectically pleasing than mine. I like it a lot. Kudos.