[Alneyan]

1) There is no mod used by default for SEIV (Zen Balance is not standard yet, though I expect it will be so soon). TDM for single player and FQM for better maps are fairly common, but they do not alter gameplay directly.

The mods actually changing the gameplay depend on what you are looking for. For example, Proportions slows down the game pace , and actually prevents you from getting all the good stuff rather quickly. PvK Balance Mod makes Empire creation less of a no brainer as well, as the best options are much more expensive all of a sudden (pretty much like Zen Pretenders mod). The Adamant mod has a feel closer to the standard game, while mods such as Devnull or Deathstalker mods tend to have a quicker pace than regular SEIV.

In other words, your favourite mod would depend on your particular tastes I guess.

2) In addition to what Brianeyci posted, I believe you should not make designs obsolete if they are still used. I seem to recall having add trouble with their ship strategies (in strategical combat) with obsoleted designs, which no longer followed their orders. I could be wrong however, since I hate strategic battles with a passion, but my natural paranoia makes me wary of this potential problem.

3) You are a very patient player. In the Colonies screen, click on "Set colony type", select the appropriate planet, and change its type. Repeat the process as needed.