I believe you get bonuses from power plants (in that they are added to base manufacturing before focusing) and get your bonus research on top of it. That's a plus. Techs give +30 SOC, +30 MIL, +10 RES. Specials give +10 RES (Hyper Computers is not included as it's so far down the tree). Evil gets slave center for +50 MIL (effectively higher in some cases depending on abilities).
I've been thinking about the best slider setup and ability distribution for my play style. I was previously running 1/99/0 most of the time and always taking +50 SOC/+50 MIL. However, this seems to be a mistake. Although I like projects to get done immediately, one has to think in terms of marginal time benefit. At some point, social projects get done fast enough that the bonus is effectively wasted; add to this the fact that ships always need to be built and techs are important throughout most of the game (once you're nearly done, you should be able to win!), but planets finish developing at some point (or at least can more slowly develop without major penalties). I have reconsidered using sliders as some people do to maximize bonuses: 100/0/0. Each planet can do the following combinations ([] indicates focus, {} indicated overflow from SOC to MIL):
[100]/0/0 (full bonus to MIL)
50/[50]/0 (full bonus to MIL/SOC)
75/0/[25] (full bonus to MIL/RES)
While the 1/99/0 setting has (approximately):
0/[100]/0 (full bonus to SOC)
[50]/{50}/0 (half bonus to MIL, SOC overflow)
75/{75}/[25] (no bonus to MIL, full bonus to RES)
Consider the case where no SOC projects are pending (it's going to happen eventually to most planets for most of the time). Note that in the second case, some (or all) MIL bonuses are ALWAYS wasted, particularly when using RES focus (necessary for an all-factory build). Assume that I have MIL bonus +80%,, SOC bonus +30%, RES bonus +60% (not so far from reality depending on picks/having some lower techs). The normal (most common) state is MIL with RES focus (to keep techs flowing) and no SOC projects.
100/0/0:
180 MIL, 0 SOC, 0 RES (MIL focus/no focus)
90 MIL, 65 SOC, 0 RES (SOC focus, SOC project)
135 MIL, 0 SOC, 40 RES (RES focus)
1/99/0:
140 MIL, 0 SOC, 0 RES (MIL focus)
0 MIL, 130 SOC, 0 RES (SOC focus/no focus, SOC project)
75 MIL, 0 SOC, 40 RES (RES focus)
Obviously these are scaled to your actual production (mp). It is clear that RES capacity is the same in either case. However, with SOC slider maxed you are not effectively able to both research AND build ships (as you have lost all MIL bonuses for doing so). Conversely, if you choose to build ships quickly, you will be unable to maintain a good background research flow. Doubling your SOC production is probably not worth losing half your ship-building capacity in the long run (since building SOC projects is a temporary need).