Family Name: Avlen
Region (NA/EU): NA
For the horse Auto-Sprint checkbox, simply have the UI remember your selection on a per-character or, even better, a per-account basis. This would turn the checkbox into a toggle so that you won't have to re-check the box every time you swap characters, servers, log in, etc.
I would say that in almost all cases of riding a horse, a player is going to want that box checked. I can think of only one reason (roleplay) where they wouldn't.
Loving all the QoL changes! Keep 'em coming!