Knowing the x15,000 ceiling before you spin
Deciding how much to stake means accepting that the bonus round may not come in your session at all. How often it starts in Gates of Olympus 1000 is not known in advance. The result of one session is random, whatever the RTP version you play, and no single session shows the long-run return.
Checking which RTP version you play starts with the game rules, because the rules are the only place the version is shown. The gap between the two RTP figures is small, but it is the detail to confirm. Read that section before you stake real money.
Deciding how large a session can get means knowing the ceiling first. The maximum win of Gates of Olympus 1000 is x15,000 times the bet, a limit reached very rarely. Treat it as the top of the scale, not as a result to expect from any session.