Sorry for late feedback, but have been busy to make a decent reply. Walker might comeback to his good form, things are not black and white, unless he had decided to follow the Delle Ali route. I agree that the 4x3x3 seems to suit your talent pool much better than the actual system.
3 at the back would make sense if England lacked physicality in the team, because usually you use 3 Cbs in order to cover more width easily so the defense can't be so easily exposed to opposition's pace when switching lanes. England rarely had problems with pacey opposition, your players are pretty much fast.
GK: Ramsdale - The english keeper in best form this season.
RB: Has to be TAA. Yes, defensively he has some issues but Trippier is doing well but not being that impressive, is it? And TAA offers much much more when in possession.
LB: Shaw or Mitchell, even though Shaw usually plays well for England. But Mitchell is doing a very solid season IMO.
CBs: Tomori and White are the ones in better form this season, but I can't see Southgate risk on this, simply because for him to make them gel it would need time, and there will be almost no time for preparation.
DM: Declan Rice is still the most complete at his position.
MC: Bellingham seems a no brainer
MC: Foden: this would be my "risky" take. Foden is disciplined and is very energetic. Him and Bellingham would provide a lot of quality to the team.
RW: Saka no brainer too.
LW: Difficult to choose, because there's no LW at top form atm. I think Sterling is the one who makes more sense overall.
FC: Kane: no brainer too.
As this is NT, it's understandable to have quality gaps in some positions, you can't just go to the transfer market and hire someone (well, except if it's an Arab federation
).
There will be no perfect teams, every team will have strong points and weak points.