Catalina to Tahoe...runs slow and hot...want to go back!

It is possible there are processes running in the background that are using significant resources. Check Activity Monitor, CPU tab (sort by % CPU) and Memory tab (sort by Memory) to see what's running hard.

Activity Monitor User Guide for Mac - Apple Support

As for going back, reverting to an older macOS is not simple. You need to boot into Recovery OS, erase your internal drive, then install the older macOS, then restore from a backup made prior to the Tahoe upgrade. Even then, the firmware on the Mac may have been updated, meaning potential conflicts and a possible need for DFU mode and a Configurator revive/restore, which would need to be done via another Mac connected to yours. If that sounds complicated and risky, then you're assessing the situation correctly.

jenbr549 wrote:

your going back solution raises my blood pressure!

So I can't simply revert back to a previous backup state?

Simply...no.

jenbr549 wrote:

Thanks. I have viewed Activity Monitor and did as you suggested, as well as shut down any programs that I'm not using currently.

FYI, the default view in Activity Monitor is only the user's own apps & processes. There are a lot of system processes as well that you don't see with the Activity Monitor's default view settings.

Plus even though you have Quit the front facing portion of an app, there can still be parts of that app running in the background which may not be viewable with the default view settings (I never bothered to check).

You need to give Tahoe time to finish processing the new OS before you give up hope there. Plus you made a huge jump in major OS versions which adds complexity to things since there has been a lot of changes in that time.

your going back solution raises my blood pressure!

Downgrading any OS is never easy, as it always involves starting over from scratch & an older backup. IIRC I have seen an OS at one time offer a brief window to revert, but I'm not sure how much faith I would have in that option (I think it was some version of Windows years ago).

So I can't simply revert back to a previous backup state?

In case @neuroanatomist's follow up "Simply...no" is not fully understood, I'll add.....with great difficulty you can downgrade.

However, I suggest you give the new OS some time to settle down. Also, if you are running any anti-virus software, cleaning/optimizer apps, or third party security software, then uninstall them by following their developer's instructions since they are not needed on a Mac and will usually cause more problems than they solve including huge performance issues. Note: Uninstall is not synonymous with delete although for some apps it may be. At the very least, the Catalina versions of those apps would likely be out of date & incompatible with Tahoe which could easily cause problems.

Also, make sure all of your third party apps are completely up to date. In addition, confirm those apps are fully compatible with macOS 26.x Tahoe.