I remember how both Max Aarons and Ryan Sessegnon impressed in the 2nd tier but they turned into "ordinary" players once they played in the EPL.
Of course, no one really knows if Spence has that extra that can turn him into a quality RWB (well, it's not even sure if he's joining Spurs).
However, as I and several others have already mentioned, there is a lack of available talent at RWB. I know many will bash me for this but I would suggest using Perisic and still get Spence (or even keep either Emerson or Doherty as understudy) as a RWB and get in either Raum or Angeliño at LWB.
Yes, I know, Perisic has played a LWB at Inter but it took him just a summer to adjust from being a forwards his whole (adult) footballing career to being a top-class LWB; so I don't he would have any problems in adjusting to life as RWB. He's right-footed and new to the club anyway.