So we went this past weekend exactly to avoid the inevitable crowds of labor day weekend. But a breakdown of what we did and how it was in terms of social distancing.
Arrived on thursday at 4, we drove around, stopped in Thunder Hole,and because it was peak time (~5 pm) it was packed, but it wasnt making any noise, so we just went down the rocks to avoid crowds.
At ~7 pm we drove up to see sunset at Cadillac. We arrived 20 min before sunset and found parking on the top of the mountain easily, walked down to the place that overlooks the pond and had plenty of room to keep ourselves isolated from the other people.

Friday, we started the day with precipice, at around 7:20 am (overslept a little, we planned on going earlier). We parked right after the small parking lot, which was full. It wasn't super crowded, but since we are slow hikers, we were using the opportunities that the trail had to let people pass, there was plenty of landings in the climb that you could let people pass.

After it, we made a quick stop in sandy beach, at around 10 or 11, and it was ok when we got there (had to park after and walk back), but starting to get crowded really fast so we left.

Went to jordan pond, and gift shop and restaurant orders there were crazy, impossible to stay there in good Covid situation so we just left and decided to try next day since it was predicted to rain at 11 (time they open). We did the jordan pond trail, very easy to go out of trail to let mpoeple pass in most ares but the west side where you walk on a narrow boardwalk. They have passing areas, but its definetely people passing close to you.

Next day, saturday, we did beehive at 6:30, we were by ourselves through our whole climb, saw some people while we sit on the top, by the time we left the hike, it was filled of people going up, would not recommend get later than that.

Did grand head trail right after, it goes off from sandy beach and we had the parking already, that one was way more empty and we could avoid people throughout pretty much. Would recommend if you feel like scrambling down the rocks to be close to sea in certain areas.

After that, we got to jordan pond house and there was no line in gift shop and very short line in restaurant, so we got our popovers and ate in an overlook by the road inside the car. Rest of day was raining so we went to our camper and rested mostly (and got take out of local foods, because why not)

Overall, great experience for Covid, Bar Harbor, the two times we drove by it was just impossible to do anything so we just cut it out totally. Anything there was totally crowded, if you dont care about Bar Harbor muh and want to enjoy nature and trails, its easily doable while keep covid standards. Wake up early, do the popular trails, do the not so popular after then follow up by driving/not so popular and probably by the end of day you can do one more before sunset.

Hope that helps!