Any decent used flat bed scanner will give you excellent results. You will be able to scan at far higher resolutions than the all-in-ones. However, unless you're doing huge enlargements, the extra resolution only buys you larger files!
Check Craigslist. Lots of people getting rid of flat bed scanners that "don't have drivers for windows 10". All you need to do is run the installer in Windows 7 mode and everything works fine. I've done it with a couple HP scanners so far. Picked up a nice used one for 10 bucks WITH the slide and negative holder, so my dad can scan in his 1000's of slides from the 60's-80's. It's giving him something to do. The scanner software from HP (free download with the driver) even corrects for the color aging of the slides. Not sure how, but it works great.
-Ken