In amplification to kryo's #2 -
Starbases and their modules are time-consuming and expensive to build, need to be defended, etc. I generally don't bother with the production boost ones unless I have a fairly tight cluster of colonies that all will be within the base radius displayed on the screen. Thus, selecting a cluster set-up in the opening game screen has seemed to me to make production boost bases more likely to be worthwhile. You might play with that and see. BTW, if such a colony cluster exists, you can build multiple such starbases side-by-side there and the colonies will benefit from the effects of all of the bases (they stack). In one game, I recall having five such colony clusters, and I built a tripod of production boost bases in the center of each one.
On your factories Q, it's basically a your mileage may vary matter. If you are doing an all-factories approach, 2 or 3 are too few for any but the most revenue centric colonies. If you're doing an all-labs approach, it's probably too many. Many players try to specialize their planets but, in most cases, having at least a couple factories is a good thing, unless you're implementing a "buy it always" strategy.