re: 5 nights in Paris or Rome

Le Relais de l'Entrecote is very straightforward: entrecôte Isteak), sauce, alumette potatoes, and a walnut salad. That's it, plus desserts. If you want french style steak, it's a good option. LINK. Several locations around Paris.

Unless you've been to Paris half a dozen times, I wouldn't bother dashing off to London for a few days. Stay where you are, enjoy the city you're in. If you need side trips aside from the WWII sites in Normandy, you can continue on to Mont St Michel or St Malo, or do Versailles or Giverny (Monet's house & gardens). Slow down, take your time, walk the streets, admire the architecture, eat diversely....don't get to one place, only to go running off to another. FOMO shoulnd't drive your leisure time.