I am even more fussy than you as I don’t even wear my wedding band, I hated taking it off when in the gym and always forgetting it, I was terrified that I will loose it one day. So the smallest watch I could find was Garmin Venu Square, it feels very light and I even slept with it last night without noticing it much. I also used it to record my bike workout along with Garmin Edge 1030 and it was pretty close, heart rate was a few beats off which is understandable compared to chest strap.
So far I feel I made a good decision finding something light, that measures basic metrics and I could stay in Garmin system which integrates nicely with Intervals.icu. Next I am testing Garmin training plan builder to see how it works with what I have in mind for my training. At first glance it looks like it has generated some interesting mountain bike specific intervals which seem less monotonous than what I was doing.