Scanning 1,500 photos to jpg - hints?

I have 1,500 4x6 color prints that I need to scan and save to my PC. I will do multiple backups along the way. Below is the equipment I use and some suggested settings. I would appreciate some expert advice before I begin this very time consuming task. I would not like it after taking all the time needed to accomplish this only to have a real expert say "Darn, you should have used THIS setting or similar".

New Dell 5810 Workstation with Windows 10 pro. 2TB ssd and 8tb mechanical drives. 32 ram. The scanner is a 3 in one new HP 8720 OfficeJet Pro unit. I can choose dpi up to 1200. I did several test scans and 300 and 600 appear more than satisfactory. After I scanned the few test pictures I immediately make improvements with Photoshop then saved them as completed. ALL these photos are family and sightseeing type pictures. Nothing commercial whatsoever.

1. Is JPG the most suitable format?
2.Are there any settings that I  should be taking advantage of?
3. For photos that are 4x6 that probably will not be printed out again but only viewed via PC or at most big screen tv is 300 or 600 dpi more than adequate?
4. Any other advice would be welcomed.
Thanks!