https://support.apple.com/en-us/HT211238

If it were me I would probably wait until the next release. Catalina had some initial problems on their first release, and I would expect Big Sur will also.

While Microsoft has its own set of issues, they usually support their OS on older machines more than 7 years old

Here is some information on that:

https://9to5mac.com/2020/12/14/should-i-upgrade-to-big-sur-on-my-mac/

Make a list of your favorite apps and utiliities. Here are a few of my current ones.

1. Pages
2. Epic
3. Safari
4. Keyboard Maestro
-------------- those are my critical ones on the Mac ---------

and some other stuff on iPhone.

Your mission:

Ask knowledgeable people about your favorites apps, widgets and utilities.

Example: 1) In the past, I used a certain aspect of Apple File Sharing. Apple removed it. For a few years, I was out of the loop. And was surprised to find a good feature was gone. 2) Apple removed iDisk. 3). I used to use RSS feeds all the time using a third party RSS reader. 4) My favorite word processor of years past -- gone. Now I use Apple Pages.

And one more thing -- Apple Stores. As for me, I used to think they were cool. Now I use a third party store only. My store is simply way better.

---------

To sum up, proceed at your own risk, after you backup everything, consult with professionals or skilled amateurs. Backup passwords especially.

I had a major disk failure once. Fortunately I was 2x backed up. During the re-install, there was another catastrophic failure which was NOT hardware related NOR user (me) related. Unbelievable. But I had the 2nd backup. Some music was lost. (not a big deal. only 3 songs are missing at this point.)

This helped me a lot when I got this 64 bit machine. I use an app called Isaac for downloaded and analyzing data from a bicycling power meter. It was 32 bit. The fix was really fiddly requiring 5 or 6 downloaded files that had to be installed in a certain way and order. If an error is made you can go back. I had to go to a previous backup and go again being careful to dot every tee and cross every eye or something like that.

I still have some 32 bit apps that are unusable. I just don't care very much.