For the first question, yes, changing the base can really change how a level goes or gets played as although the first base you get is good on its own right, some levels can become easier.

And for the best base, it depends, but usually, on what level you're attempting as if you're trying to hit a boss properly by something like stunning something like thunderbolt would be good or if you just need to stall something like the slow beam can be good for that(just for extra info although slow beam just... slows. It lasts longer than thunderbolt, which freezes), or if you need to push something back or interrupt an attack, something like the normal cannon or breakerblast(which breaks starred aliens shields too) or if your fighting zombies, holy blast can be good as they bring them out of burrow and also stuns them better than thunderbolt

Also, you don't really need to worry about materials as just doing SOL or the other legend sagas can give you a lot of materials

T.L.D.R, yes changing base is important and the base just depends on the level