Downgrade from Big Sur to Catalina, yes or no?

Agree with @Ptaxey to try the Maximize Battery Life and Lifespan option.

If downgrading, remember, the only way to do so involves deleting Everything. It can not be brought back unless there is a Time Machine Backup and / or a pre-existing Bootable Clone.

Apple offers a proven and test method to create a Bootable USB Installer over Here. Set aside several hours for the process and have a reliable and fast Internet Connection preferred by Ethernet connection.

Hi!

Check the Apple's guide: Maximizing Battery Life and Lifespan - Apple

If downgrade is the case, there are at least two options to downgrade: you may use Time Machine from Catalina backup to go back (that is not suitable for you, as far as I see), and second one is downgrade using bootable OS installer.

Don't forget to backup anyway!

There is also an article with more precise instructions.

Hi,

I've had a similar problem on my 16mcb pro and after about 3-4 days on Big Sur my battery was down from usual 7-8 hrs to 1.5-2. Really disappointed, I downgraded to Catalina using the external usb method. Yes, you'll need to start from the beginning but it's actually been painless and not that time consuming once you follow instructions of which there are plenty websites out there. I'd recommend it and forget about Big Sur at least for 4-6months. It looks and feels like a toy rather than a tool for work tbh. For me (working photographer) it's not what I need... I need reliability and speed. I've got a feeling Big Sur is built for M1 but I, and you shouldn't neither, don't want to be an early adopter. Well, unless you have no bills to pay and time to play with, well, toys:)

Same issue, battery drain in 2 - 3 hours and the fan constantly runs. I will be going back for use with Serato DJ Pro.

The Battery drain will be that way for a while. Big changes happened due to the upgrade to Big Sur. The new OS must reindex everything and settle down. Give it a few days and suggest using it on charger during this time.