No idea why you are getting downvoted.
A great middle-ground is EndeavourOS. It has a great installer. It makes pretty decent choices. You have a pretty much 100% pure Arch system after install. There are only a couple dozen EndeavourOS packages and most of them are utilities. You can remove all the EndeavourOS stuff in a couple of minutes if you really want to and comment out the repos. Not sure why you would. Just pointing out how vanilla it is.
Why not Arch? The Steam Deck is Arch. Seems like a good choice.