Accept that the bonus timing stays unknown
Deciding whether to keep spinning Jewel Rush while waiting for the bonus means working with an unknown. How often the Free Spins round comes is not known in advance. Each session is random, so one session can bring a long dry run or two bonus rounds close together, whatever the RTP. The RTP describes the long run, not your next hour.
Choosing which RTP version to play starts in the game rules, not in the lobby. Royalreels shows which RTP version runs on Jewel Rush only there, so open the rules before your first spin. Reading them tells you which version the tables on this page describe.
Setting a bet on Jewel Rush starts with the ceiling, not the top prize. The maximum win is x5,000 of the bet, and that ceiling is reached very rarely. Plan each session around money you can afford to lose.