After reading many good results posted here, I decided to take the plunge and move to OpenCore. I was a bit hesitant after a first pass read of the Dortania's Install Guide, but I decided to follow it carefully and give it a try. After a lot of editing to EFI folder content, I figured there is no chance I did everything right.
Wow, was I pleasantly surprised! The install went perfectly and now I have Big Sur 11.1 up and running. I used my existing SSDT.aml from Catalina. I also tried AppleALC to work with Realtek ALC221 I but could not make that work. However, since I switched to using an external USB sound device a while ago, I did not pursue this much further. I went go back once and made an update based on the Guide, but no luck. So far everything seems to work as well as in Catalina.