FWIW, I found the Whoop useful for about 6-9mo. One of the biggest revelations was that I was actually getting more/better sleep than I would have guessed (sorry to bring that up in this thread). The other big take away was that I wasn't eating anywhere close to enough on big days and overeating on easy days. And it confirmed my suspicions about alcohol.

I've noticed some problems falling asleep if I start a weights program. The first few weeks are rough. Once I'm settled into it, it's all good. I think this may be similar to what KonaSS describes above.