the intent there is to make them "still the same unit", it also helps to possibly avoid issues with health scaling, but as far as I know this works fine for CS promotion.
I think the ranged version is a bit too good still, as it should be on par with the melee version. Probably some armor change would be good for the ranged version.
yeah this has been an ongoing problem for plenty of windows players including myself, so I mostly use keys to pan the camera. There is an issue written for it: https://gitea.wildfiregames.com/0ad/0ad/issues/7673#issuecomment-115591