First time floor refinisher here and I need you experts to double check my steps please.
I ripped up the carpet to find about 700 sq ft of red oak. It’s mostly unfinished, but there is about 250 sq ft of a stained and poly area.
I plan to sand everything using a U-Sand (too scared of drum sanders). Then staining, then finishing with Bona Traffic. Please check my steps below:

1. Sand with 24 grit. (Since U-Sand machines are not nearly as powerful as drum sanders, I’m starting with a very rough grit to make up for the under power). Vacuum
2. Sand with 40 grit. Vacuum
3. Sand with 60 grit. Vacuum
4. Spot fill all nail and staple holes. I did some experimenting with fillers (Timbermate, Parks); I found that Famowood Latex Wood Filler works the best for accepting the color stain I’m using.
5. Final sanding with 100 grit (or should I screen with a buffer?).
6. Vaccum and tack
7. Water-pop floors using purified water and a sponge. Just enough water to dampen floor. Wait for floor to dry overnight.
8. Stain with Minwax English Chestnut stain. Letting it sit for like 5 mins before wiping off.
9. Give plenty of time for stain to dry completely, at least 3 days.
10. Apply 1st coat of Bona Traffic Using Bona Roller and Padco Pads
11. Abrade floor with pole sander and 220 grit screens. Vacuum and tac
12. Apply 2nd coat of Bona Traffic Using Bona Roller and Padco Pads

I would really appreciate any advice with my plan. Thanks in advance!

skip the 24 grit. You don't want to put any scratches deeper than necessary that you will need to remove.
try 50 grit for a start. an edger can do spot sanding where you need it.
plan on using a buffer with 100 grit with a driver pad after the vibrator.get a carbide scraper for the corners. hand sand with 80 grit to blend the different machines together.

Hi, i dont recomend that kind of machines, that machines is for the last paper. You should rent a drum sander or a belt sander and start with a 36 paper or 40 then 80 paper and then with a buffer a 80screen and after that a 120 screen. Between steps you should vacum always and you will get a good result.
When the sanding proces is done you can stain the floor, wait 24 hours, firs coat of sealer and let dry, then Traffic let dry, buff with 150 screen 150, vaccum it again, clean it with a damp cloth and apply the last coat of Traffic. Really sorry for my english, i know im bad bye

Hi, about the stains i only know Bona create stains, its the only good quality stains that de can get in Argentina and its really expensive!! 100 dollars per liter and Traffic 335 dollars a gal. Bye and sorry for my bad english.

If your floor is relatively smooth and you just want to remove the finish you can use the square buff type of machine to sand. You need to be careful when you stain the floor because machine marks show up if you don't prepare the surface evenly.