You'd be stuck at 15W max on the N20U since it doesn't have the PPS protocol.

This is the charger I've been using for my S20 (which I returned after 2 weeks and waited for the Note 20 Ultra I have now). And it works great with the N20U also. But keep in mind it won't fast charge 2 devices at the same time like the Samsung charger will. So if you need one single charger for both devices at the same time, the Samsung one would be better for that.