I used Variety for years, nothing wrong with their pictures or their scaling, never seen a single low res pic or grain or size issue.
That said I have no idea the source quality of your own pictures...unsure you will get the granular detail of scaling you require in budgie/settings/display however Variety might offer minor scaling as well.
What's the program that will manager your particular pictures the best? No clue.
Will be trial and error.
This article https://www.ubuntupit.com/best-linux-wallpaper-changer/ lists:
Wallch, Wallpaper Downloader, Shotwell, Webuilder, Wallpapoz, Wonderwall, Slidewall, Drapes, Komeribi, WallpaperTray, ---a nice afternoon at github!
Which has the microlevel control you need is hard to tell.
this also suggests you can get what you want with gnome-tweaks
(https://unix.stackexchange.com/questions/652663/how-to-correct-the-size-of-gnome-desktop-wallpaper-image). If Variety goes by desktop settings then maybe luck