I had a very bad AF last year after pericarditis (may have been linked to getting covid!) but persisted with my walking (which I'd done for some years). I had to slow down as my pulse was coming out at 140+ without some care! And couldn't go up slopes any more.
Had an elective defib (1 shock) and this cleared up the AF mostly but pulse still prone to extra beats and so on. But after a year, I'm back up to 10 mile walks with hills included. Big improvement from my little, slow trips down the road last year.
I use an HRV (heart rate variability) app on the phone to keep track of my fitness/energy/stress levels morning/evening. When the app starts going red/orange I take it easy and do meditation with deep breathing which settles things down pretty quick.
I miss the odd day walking if it's pouring (I do short squats and dumbbell lifting sessions if the weather's bad) but otherwise walk everyday at least 2 miles, a lot more on the weekend. Keeping fingers crossed. And still experimenting with various apps, self monitoring really is the future of maintaining good health I think.