I am in the process of switching my Tiagra 4700 road (drop handlebar) bike to 1x. I will start with a cheapo 1x narrow wide 40T or 42T chainring.

I could stop there but as I now only have mechanical Spyre disc brakes I would also want switch to hydro brakes and shifters (briefters).

I already bought BR-RS785 calipers as they are the only ones that fit Post Mount attachments.

As far as shifters I could go with new ST-4720 Tiagras (10spd) or newly announced GRX ST-RX400 (10spd) but for some reason (probably because they are older) I can find ST-RS685 (Utegra) or ST-R7020 (105) cheaper.

The problem with Ultegra and 105 (7000) is that they are both 11spd.

However I read that the pull ratio for the latest Tiagra 4700 is the same as for 11spd. Based on that my question is whether I could buy just the 11spd shifters (and restrict the RD to just 10 gears) for my current setup and stick with 10spd RD, cassette and chain?

If not - would additionally changing only the RD to 11spd (while staying on 10spd cassette and chain) - make things any better?

Thanks for any advice.
P.S. My 2 sets of wheels are both 11spd compatible so I know I could switch to all 11spd - but then would also have to by 2 new 11spd cassettes and an 11spd chain.