can we use it to boost memes ?
Promobot has no restrictions related to memes.
Do you mean you will vote maximum to the amount sent ? So if I send 5, you vote max 5 ? What do you mean by does not give votes worth more than the amount paid for promotion.
It mean that if you send a 50$ worth bid the projected combination of STEEM and SBD reward from the vote at voting time should not be worth more than 50$.
It can varies if market prices and SteemPower global utilization changes.