I think the biggest mistake in most brains are that the rtp is linked to any other player, betsize or anything else.
It's not that complicated that you think because it's just math and the rtp is always a long term theoretical value after millions and billions of spins and not for a single player or based on any betsize, coin or whatever.
In most cases, the slot doesn't know anything before the spin and after the spin (only the progressive slots are difficult and have a "mind" for few spins because of progress features). Additional the manipulation is not a thing that you can do as provider, of better what you never will do when you continue work in this business. It makes no sense to change anything on a permanent and save earning math formula. The Casino will win, always.
That's it. Nothing more, no magic, no balancing between players, nothing.
If you want to deep dive in the math, functionality of rng and many more, you can check as example this video. He explain all basics in a really easy way.
Greetings from a dev that worked few years with the Gauselmann/Merkur Group
Edit: If you think that real slot machines works on different way than online machines, no, it's the same shit, just online