The developers have said before that they're still optimizing pathfinding (this is the reason for units being able to move through each other and the cap on how many units you can select at once), but that isn't usually the problem for people who aren't getting good frame rates. I suspect they haven't put a lot of effort into making sure all the effects run well on low-spec computers yet. On most desktops the game runs at a constant 60 FPS and doesn't have problems with CPU bottlenecks. Early on you could tank the frame rate by trying to place a building without there being any valid spot to place it, but they fixed that.

There are a few graphics options you could try turning off to reduce the strain on your graphics card, but you might have tried it already. Bloom, screenspace ambient occlusion, high dynamic range lighting, gibs, as well as turning down the shadow quality slider. The shadow slider is probably the most important option there. You can completely disable shadows by moving the slider all the way to the left. If you haven't tried it yet, give that a shot, nice soft shadows are expensive to render and probably not a good idea on a mobile GPU.

Hopefully a dev answers your post, they've been kinda busy lately and not able to reply to every post.