iPhone 11 and MagSafe charger

MagSafe / MagSafe Duo will work fine. iPhone 11 will only charge at standard Qi 7.5W since it doesn't support MagSafe (i.e., >7.5W - 15W).

Anecdotally, I use a 7.5W Qi-certified charger in my living room and the MagSafe Duo in my office, both work just fine except you get a little more convenience (e.g., magnetic "snap" and alignment) and charging speed out of MagSafe.