Find the RTP version in the rules
Deciding how long to play is a choice you make before the first spin, and the game gives no sign of when a bonus round will land. How often that happens is not known in advance. The result of one session is random, whatever the RTP says, so a session can end well above or well below where it started.
Before you rely on a return figure, check which RTP version Casinox runs. That version is shown only in the game rules. Read the rules before you start, and treat the version named there as the one that applies.
Choosing a bet with a big win in mind starts with one fact: the maximum win is a ceiling, not a target. Gates of Olympus pays up to x5,000 of the bet, and that ceiling is reached very rarely.