100billion is the population cap.

Trying out building a few 25+ Billion planets right now. (they're PQ30 planets)

I'm not sure if i'll get to 45B by the end of the game, but i'm curious how they work out. (kind of a game within a game) (one has a good farm bonus, and the other has 3 advanced farms.)

The sad part is I think it works out for money better to stick with just one farm, and go with all stock markets. To me, that's something that needs to be rebalanced. Even still I like to get big planets to at 25B for troops and metaverse score.

Tax money from population is calculated using the square root of population, also the effect of morale bonuses decreases as population increases, so one farm might need one building while two farms will need 3 or so. All in all I find it much better to just stick a farm and morale building on every planet above size 9 or so.

The game I just finished, I sent hordes of extra transports to fill up one of my pq30 planets. I finished the game with around 70B making around 5800 BC. (eco capital and mind control center with 78% taxes)

what is up with people and 70+% in taxes, good God, I have never went over 50% even when I am at the beginning of the game when I need it most. Once I got my economy going I hover around 25% and still take in 1 to 1.5k a turn. Once I went as low as 10% making only a few hundred just so i can be happy that I run an effienct govenemt

The point is to have a high tax rate (=higher income) while still keeping the population happy. If your getting ~1.5K at 25% you'd be getting ~4.5K at 75%. If you can do so and still keep your population happy then you can use the extra cash to buy improvements so your planets develop faster. You can also use the cash to buy and upgrade ships. Extra money is as good as, and somewhat more flexible than, extra production, the only thing it can't really buy is research (unless you count buying tech from the AI's).

Throughout my current gigantiac suicidal game I've been operating at 100% approval (giving me the 100% pop growth bonus) on every planet (currently have 226) with a tax rate of 79%. Every planet I have has a single advanced farm for a total pop of 15B (except civilization capitals that have 20B) without a single morale building on any planet (other than stock markets). I do have two morale resources that I'm mining (+44% each) as well as most of the morale wonders. At this point I'm generating ~60K bc/turn. This is a big help in large invasions. I'm taking over ~25 AI planets a turn using the Mini-Soldiers tatic (500 bc each) to minimize the number of troops I need. I also have plenty of money left over to buy 10 or so Industrial Sectors to jump start the production on my newly accquired planets. If I had to hold my tax rate to 25% to keep my pop happy then I'd only be getting ~20K per turn and be much more limited in what I could do.

Actually, at the begining of the game during the colony rush is when you most need the 100% approval bonus for early pop growth. That's the time I set my tax rate to ~15% and go into deficit spending from my initial 5000 bc plus whatever my flagship can get from anomalies until my colonies begin to become profitable.

what is up with people and 70+% in taxes

I've done low-tax games before. Actually, they're militarily a good idea, since you can put asstons of people on your worlds with much less trouble. Still, the high-tax method makes a lot more sense (I'm paying for pretty much everything my citizens would need or want, so it's actually a good deal for them going by the "realism" argument), and it requires much less micromanagement (one advanced farm and one VR center per world, almost no exceptions; saves on the planning).

On the original topic:
I had two of these. My population growth was "Don't Ask" and I supplemented them with transports, so it only took a few years to fill them.