My first piece of friendly advice, step away from your computer. I am a notorious seat map checker as well, but only a few days out from my scheduled departure date. You will drive yourself nuts if you keep this pace up for the next 3 months. These seat maps are extremely dynamic so don;t worry about what you see today or even in the next few weeks.

As for 20F, the emergency slide juts out a bit so instead of being able to stretch your legs straight out, you have to angle them slightly to the left. No big deal really. If you were in 20A before, this seat also has the slide jutting out into the aisle as well. That being said, 20ABCF are the best in Comfort+ on a 75X configured bird, so you will have an abundant amount of legroom no matter what (except for 20DE).