3. How would you describe your play-style in multiplayer strategy games?
This is hard to answer, as it entirely depends: is the game coop with other people (players vs. ai)? Team v. team? Player v. player (freeform/freeforall)?
It also depends on the structure of the game. A game like AI War requires a balanced approach: massive offensive force that is used for defense when the AI waves come (in addition to massive defensive emplacements). Doing anything else will get you killed.*
Game like Sins of a Solar Empire? Light defenses, massive offensive fleet (within reason, the best way to get fleet size is to improve your relations with another empire such that you get the +800 fleet supply partnership bonus--800! FLEET SUPPLY! It's worth as much or more as the first three levels of fleet logistics combined without the downsides (-39% income)).
*Unless you get lucky and get a system with a gravity drill on the far side of the system from the AI wormhole and then drop a military command station, which teleports the invading units away from the station faster than they can move back into firing range (due to the Gravity Drill enforcing a max move speed of 8 on everything; for reference, a "largely immobile" force field generator has a speed of 22).