Going to be best to check a guide as no one size fits all, depends on power your trying to save, type of game etc, your silicone lottery, temps etc this thread could be a place to start: 3080 Undervolting | Overclockers UK Forums
For me, I have a number of profiles set up designed to ensure for the game in question I am not hitting my power limit on the FE model which is what causes problems, for most games playing atm, I use 1.0 volt @ 2100Mhz which works fine and means it sips around 300w or so in something like AC Vallhalla.
For more power hungry games, will cut the voltage down as will hit into 400w limit in something like CP2077 at 1v. So usually 0.9v @ 2010mhz or something.
Hmm, could try rolling back, I think your spikes is not massively unusual, but if it was more settled before, could be worth trying. I am not on latest drivers myself, rather on 466.11, so not sure if newer ones have introduced anything more pronounced.
So you dont think that the spikes lasting a good 15-20 seconds before dropping then increasing again is unusual? And if when the "spikes" hit, is only drawing around the 100W mark, wont damage the card at all, do you think?