Waiting on a bonus that may not come
Choosing a stake before the first spin means accepting a result nobody can predict. How often the bonus round arrives is not known in advance, and the outcome of one session is random whatever RTP version is in play. The RTP describes what the game returns over a very large number of spins, so it says nothing certain about the spins a player makes in any one visit.
Checking the RTP starts with the game rules, because the version running in the lobby is shown only there. Several versions of this series exist with different RTP values, and the rules state which one this game uses. Read that section before the first stake is placed.
Judging a slot by its top prize means aiming at the ceiling, and that ceiling is reached very rarely. The maximum win of Big Bass Splash is a multiple of the bet, so the cash amount depends on the stake. Use the figures on this page to work out what that ceiling means at a chosen bet.