What I've done and where I'm at now. I am not condoning these steps as the correct process, just what I was able to build off of based on other resources online.
1. Upgraded my existing 8.2 DBs using the 9.3 upgrade package on my 8.2 instance.
2. Stood up a 9.3 CMS-only instance
3. Pointed the conn string configs to my upgraded 8.2 DBs. At this point the Sitecore UI loads up and I see the content editor with all my items. Sure nothing is functional or able to be published, but at least it's something.
4. Analyzed and reorganized the config files. 8.2 to 9.3 has some good reorganization of these files based off layer changes. UI still running fine after these adjustments.
5. Pulled down our solution and upgraded the dlls to 9.3. Did a ton of compares on the config files to better understand changes and customizations my team has made over time.
6. Sorted out build errors.
7. (Im stuck here) - working through a rabbit hole of runtime errors based on many factors. I've gotten past some of the more significant ones like using the Solr instead of Lucene and disabling features we don't use.
This has truly been a terrible experience. I have less than 1 year of experience with Sitecore and I'm the only developer working on this upgrade. We have 5 sites and I fear this will be the end of me.
Sorry for the delay. I got put on another project but now I'm back to it. The fact that Sitecore docs exist for upgrading from versions 8.1.0-9.0.1 to 9.2 (or now 9.3), led me to believe that was an ok course of action.