Casinodaddy, Letsgiveitaspin and Jarttu84 are 100% legit. Jarttu84 has many videos showing his bank statements etc.
I’m a mod for Casinodaddy, and have been watching for a long time, and talked to them a lot. They play a lot at Leovegas, where they get a 100% no sticky bonus up to 500% euro with 20 euro max bet and no restrictions on buying bonuses, so that lets them play with 1000 euro, and they get that bonus 3-5 times a day. Lately they have been losing a lot, but losing 500 euro a time instead of 1000 is huge, double the playtime as well.
The money they play for is real, the cashouts and deposits are most definetly real. The only edge they have is the almost limitless supply of deposit bonuses.
All streamers get some money for streaming, regardless of what type of games they play, slots or normal games. It’s their job after all. Combine that with the deposit bonuses, affiliation etc and it’s not that hard to see how it can be done.
I don’t watch the others you named, i don’t know anything about them, so i won’t speculate about where their money is coming from.