I'd try the reboot with no external drives so the computer does not have to poll the extra drives. I have seen cases where an unhappy external drive enclosure slowed overall performance.
Is internal storage original or a latter upgrade? Sometimes, upgrading to an aftermarket SSD can after a while start to show slow drive performance if TRIMforce is not enabled. Beach-balling can be a symptom of underperforming storage. There's a safe way for you to show us you drive performance and other potential configuration issues.
If you want a data-driven evaluation in this setting where we can neither see nor touch your computer, please post an EtreCheck report. We can quickly and within the limitations of these forums help you determine what issues are at play without our playing a protracted game of "20 Questions" with you that could go on for days.
EtreCheck Pro is available here:
https://etrecheck.com/index
The free version will do nicely for this purpose, although the app is worthy of our financial support.
We can see hard data about drive performance, software issues and interferences, and RAM usage. Etrecheck is the development of a long-serving and trusted ASC contributor. It is a reporting app, not a "fix-it” app, expressly for displaying information in these forums to help us help you remotely. It will not reveal any personal or secure information.
To avoid a garbled or hard-to-read report, please see this excellent user tip on how to post long text reports like EtreCheck's into a forum response:
How to use the Add Text Feature When Post… - Apple Community
Please post the entire report. What seems insignificant to a new Etrecheck user can speak volimes for those of us who have reviewed thousands of those reports
