Welcome to the board!
A very simple but at the same time difficult question from me:
Do you believe he is good enough to play in the PL, and to be a positive difference for us?
Have fun over here, nothing is as good as a good ol' glory-glory discussion
Simple answer from me is, I believe so.
Just like all the scouting, I am positive that Spurs have done the research for awhile. There have been numerous rumors for the past seasons that Spurs were interested in his service, at least in Korean media.
While I don't think he will ever play for Barcelona, Madrid, Bayern in his career, he has potential to be a star for clubs right below that tier IMO.
There's more room to grow for Son, but still he is well-suited for the fast league like PL.
Two things I am worried are: inconsistency (used to be worse but still not Mr. Reliable), and his upper body strength (his frame is small although it is bigger than it was at HSV)