[capnq]

Multiplex tracking:

In Tactical Combat, you have to manually turn off any weapon that you don't want to fire at a target. Click on the weapons you don't want to fire at the first target; only the weapons with a lit-up background (and a non-zero chance to hit)will fire. Then click the weapons for the second target to turn them back on; repeat as needed.

In Strategic Combat, you can't control the firing; what Multiplex is good for there is that when one weapon destroys a target, any remaining weapons can fire at another. (I'm not sure how often firing and damage priorities are checked; Multiplex might let a ship change targets that way without necessarily destroying it.)

Mounts: depends too much on the situation to give my opinion.

Climate Control: I don't even use that much in solo games, let alone multiplayer; there are usually several other technologies I have more urgent need for.

Research & Intel:

If you don't spend all the points you're producing each turn, the excess is lost. This is especially important on the first turn, when you have the starting resources from the game set-up to spend. Repeat Projects has no effect on this; it just adds completed projects to the end of the queue again.

If you use Divide Points Evenly, excess points beyond what's necessary to complete the project are lost. I'm not personally convinced that you can waste enough points this way to be significant over the course of the game, but I normally micromagage it and turn off DPE when a project is near completion.