Moreover, if a marketcap is too high at the beginning, the potential growth of the investments is limited.
This is very true.
Sometimes devs can't stop their greed and it makes investors lose.
If you have a good project you will probably get tons of money but if you don't put a max cap for it, only you will win and investors won't.
This depends on how fast can the project scale up. If organized properly, even high cap investments can moon after ico in no time.