If starting, I would go mirrorless, as the trend/future is certainly in that direction. The lenses for mirrorless seem to be sharper on average than those for a dslr. If wildlife is your target, a crop sensor like in the Olympus, Nikon Z50, Sony Alpha 6500 would be good. If landscape, I would go full frame.
Canon is set to release a camera EOS R5 that is being touted for video. Not much is said about the sensor specs yet.
Nikon has the Z series- Z50, Z6, Z7 so far.
Sony is also very well thought of for mirrorless.
Get good glass over megapixels.