Hacksaw for long time catered their games via Relax and Relaxs does not allow to adjust RTP. Now they are going direct integrations as well, so I am not entirely sure.
Related to Relax - an update. Unfortunately, Relax Gaming introduced lower RTP settings model (around 94%) earlier this year. Bad news, since Relax is a top-notch provider. If you are playing Relax slots, be sure to double check slot RTP to be sure its a default/top one.