Manufacturing and research - yes. The capitals mulitply the output of all the factories or labs on that planet. Just pick two of your biggest worlds.

But the economic capital doesn't multiply the output of banks, it just acts like one big bank. And you can't really stack too much population on one world, so don't even try. The Home Planet or any high high Quality world with at least one farm will do fine for this.

Hi!

Yes, many:
1) outputs from buildings are additive, but bonuses from manuf. and research capital are multiplicative (not from econ capital though). So each lab on a planet with the research capital will produce twice the stated TPs. It is also quite easy to support such a planet with a bunch of econ starbases with production-enhancing modules. With carefull choosing (and some luck) you can even cover both capitals with the same SBs.
2) any planet can be money-producer, but bigger planets are better, because the effect of a new market(s) will be added to the the exsisting ones, and on bigger planet it will add stated percent to much bigger base. Quite a common approach is to have a significant percent of planets dedicated just to money production, up to 90%+ with "mostly buy" strategy in galaxies with hundreds of habitable planets.
3) less micromanagement, because only a small percentage of planets acutally produces ships that need to be directed.

BR, Iztok

In DL 1.2 neutral was my favorite because of the NLCs and auto-terraforming. Then they increased the cost of NLCs from 300 to 500 and required that you research the terraforming techs. In DA 1.6 I'm playing as evil and liking the MCC(for a 100% economic bonus), ASC(for a 50% military production bonus), and powerful evil weapons available early in the tech tree!

Edit: Sorry, posted to the wrong thread!