Pretty much the same experience I have, I get anywhere from 5 to maybe 20Mbps down during the daytime, but late hours such as after 10 or even Midnight I get mid 30Mbps down and saw just over 50Mbps down a couple nights ago and that is rare. Note, I am on the basic plan, 4G LTE area only, no 5G. My upload speeds are not great and just over 1Mbps at any time I check.
I am between towers about 8 to 10 miles so I am borderline on 1 to 2 bars so it impacts speeds. When I run to town and within say 2 miles of a tower I ran over 150Mbps, but funny thing is I can check it a minute later and get 10Mbps. For the most part speeds are in the 80Mbps range on average that close to the tower.