I recommend having an installed steering compass of known error regardless of how much electronics you have. NOTHING will give you a better idea of what is happening to your boat's head as it yaws frantically about at anchor in a blinding rain and strong winds. And if you break free and need to try to get her head up into the winds to survive, you cannot possibly steer properly into the storm without a compass because the electronics will be too slow to give you heading info.
I remember a time when I was running through some oxbows at night watching the radar as we went. I was not having much trouble until we noticed a layer of unexpected fog lowering just above the pilothouse. Soon it was below the PH, and I was trying to steer with the radar, but its speed of refresh was not fast enough to keep me for oversteering or understeering in the tight turns. The compass was the saving grace as I began to use it to determine rate of turn. It was installed where best seen, had no battery to quit, and it was adjusted properly and not something you pull out of your pocket, fumble with buttons to find the app, and slap down on the dash possibly near something ferrous.
I turn the chart plotter and AP on whenever I get underway, no matter how short the trip, but I never have to think about the compass. I always compare it to the indications on the AP and the plotter to ensure all is well. If there should ever be significant disagreement, I'd slow/stop until I had it figured out. When the fuse blows in the night and the electronics quit in the middle of a night time run into the bayou, I know the compass courses home and can get there fine as long as I can look out at the lights to get a general clue as to position.