I usually try to avoid answering when questions are too subjective. Everyone has their own preferences and expectations when they travel, plus their own baggage and past experiences. It gets really tricky and honestly kind of pointless to give super personal opinions. What works for me might totally not work for you.
That said, let’s make an exception with a couple of short notes:
Time of year
Don’t fool yourself thinking you’re visiting “off-season.” It’s been many decades since Barcelona really has an off-season. Sure, there are fewer tourists than in August, but you can still find places crowded, especially the spots everyone wants to see. Proof of that is that at the most popular attractions, tickets are mostly sold online in advance—no ticket booths anymore.
November is a bit chilly in Barcelona, but compared to Maryland, it’s warmer, with temperatures around 10°C (50°F ) in the morning or evening and about 16°C (60°F ) around midday, and most importantly, it tends to be sunny with very little rain. But be prepared for a surprise: l'Estiuet de Sant Martí (literally Saint Martin’s little summer), a nice little local weather phenomenon in Catalonia. It usually happens around mid-November, right after the feast of Saint Martin (November 11).
During this time, you can get a few days of unexpectedly warm and sunny weather, almost like a mini-Indian summer. In Barcelona, this can feel like a pleasant surprise after the start of the cooler, cloudier November days. People often take advantage of it to enjoy outdoor terraces, strolls along the beach, or a last few swims before winter. It’s short-lived, though, typically a few days, and then temperatures return to normal autumn levels.
Gaudí
Unless you have a really special obsession with Gaudí, doing too much of his stuff can get overwhelming. I’d mix it up with works by other architects. Barcelona’s Modernisme scene left amazing buildings all over the city by dozens of architects besides Gaudí, like the Palau de la Música Catalana or the Sant Pau Modernist Centre among others. You could also mix eras and styles. Barcelona has over two thousand years of history, from Roman times to Gothic, Baroque, Neo-Modernist, and 2 avant-garde.
For example, you could visit Park Güell in the morning, walk down to Gràcia for lunch, and then hit the Sagrada Família in the afternoon. If you’re not into walking in the park, swap Park Güell for Palau Güell, the Count Güell’s house and Gaudí’s patron: https://community.ricksteves.com/travel-forum/spain/infox-in-bcn-visiting-the-sagrada-familia-and-then-park-guell-or-the-other-way-around
Casa Batlló or Casa Milà, also called La Pedrera? I’d pick just one. Both are spectacular and have their own highlights; you’ll enjoy either.