Agree with most answers; again another eras post. Let's look at 1922 Walcott against 1922 Dempsey. Let's look at 1952 Walcott against 1952 Dempsey. I love "Mr. Cream"! (my fav band by the way) but Jack would have searched and destroyed at some point.
If JJW wants to win and boxes the way hes capable off then he wins on pts in my book. However, the question remains in my mind, does JJW have the discipline not to get involved so to speak, to do so. Im not so sure he does, but hes certainly more than capable of doing it
Walcott would be crowded very early as although slippery he did not have the leg speed to avoid Dempsey charges. I don't think the fight goes three rounds.