This sounds like a question for Jingles, teacher of Jonesy.
Haha!

That is a malicious lie! Well... he introduced me to the assimilation cap table, but that's all really!
Anyway...
Yes the size of the Aristocrat POP does make a difference. The culture does not, however.
As for the size, well I believe it works with the usual tier system, due to these results from a quick test where there was 40,000 national-cultured POPs working in equal sized cattle ranches in a vanilla Revolutions game:
Code:
[U][B]Number of Aristocrats[/B][/U] [U][B]Output (units)[/B][/U] [U][B]Money (£)[/B][/U]
0 0.32 0.66
1,000 0.32 0.66
40,000 0.33 0.69
80,000 0.35 0.72
Moreover, the bonus granted is applied using some kind of tier system. That is, 100k POPs would be 100% efficient, etc... (can't remember the exact numbers for the tier system).
Actually, the VickyWiki does give good values for aristocratic effect on production bonus,
here.
As for capitalists, they will just be there to get taxed for an uncivilised nation as they can't build factories or railroads when in an uncivilised country.