You have picked two interesting cameras…
EOS 250D is a great entry level DSLR camera with lots of features and capabilities. Unfortunately DSLRs are now a dying breed and no longer being developed. So you would be buying in to a dead end system as a first purchase.
EOS R100 is a mirrorless model, but actually derived from an older M series mirrorless model. As such though it is "mirrorless" and has the RF lens mount for compatibility with RF and RF-S lenses it has a number of compromises in compatibility and feature set. The AF system is the least capable of any R-series camera and there are some compatibility limitations with certain RF lenses.
I would suggest that the EOS R50 is a much better model that delivers significantly better autofocus than either of the two models you listed. I would choose this one over both of the other cameras.
Brian
EOS specialist trainer, photographer and author
-- Note: my spell checker is set for EN-GB, not EN-US --
