Totally get that on the variability in courses! That’s where it’s nice to have some kind of reference point that you can look at very briefly, know where things stand, and then get the eyes right back on the terrain. I’ll use NP (normalized power) for stuff like that because it’s a good representative metric to tell me just how hard I’m pushing (especially on variable courses like our local short track XC course). I’m able to look at that NP value and quickly asses how things are going - if I can push more, or if I need to dial it back.
On the other hand, to a point that has come up a few times already - how much can we “take in” and process while on the bike? If it becomes a challenge to think about our own effort, our fueling, hydration, and then on top of it what all those numbers are telling us while we are trying to pay attention to the terrain ahead (and other racers), it might just be too much. It’s just as useful to leave the data behind and ride by feel at times - the body is an exceptionally good power meter! We just have to learn how to listen to it and work with it 