looks like the difference between Fullscreen Quality Setting High vs Low.
In C2 you had it set to high (which gives you full res of your tilemaps)
In C3 you have it set to Low (which renders at the Viewport Size specified) (and will be better performance if you have a low viewport resolution but will also be blocky)
check your settings.
edit (although the buttons look crisp in both so maybe not this)
anyway yea just verify to your project settings are the same in both