None of those RB's can defend. you don't appreciate defending FB's because you've had the 2 of the best over the past 15 years, you take it for granted. AWB just needs to complete the cipher and learn to play CB so he can be Roadman Thuram.
Reece has improved a lot defensively. Gets tighter to his man and rarely lets them get the turn on him - he didn't have that in his game last season. I expect him to get better because he is physically capable; he has decent enough pace and is ridiculously strong.
AWB may have an outside chance as the right sided CB in a 3 but once Southgate goes and another manager comes in playing a back 4 it's over.