How to access full resolution photos from iCloud?

I think some things are in iCloud, some in Drive. Want full resolution photos, but automatically ticks on optimize storage? I have a mess in trying to disconnect from cloud, just store what I have up there.

I have a real mess after multiple erases and reinstalls. Mac Mini Catalina.

I know we moved things to iCloud Drive, but from my understanding, once moved, it's no longer in iCloud Drive, no longer saved up there, only on my computer? Or is it the other way around? I'm confused, as I want to save my stuff to 2 externals and not have them go poof off of them. But I'd, ALSO, like to have all of my current data saved up there as well before i uncheck ALL boxes, including iCloud Drive. After that I'll manage my backups myself. Once moved to iCloud Drive, is it even possible to reconnect everything to iCloud automatically? Or is it permanently stuck in Drive?

It appears some things are in iCloud, some in iCloud Drive, probably because at times I would uncheck all boxes, including Drive. I'll get prompts 'Do you want to remove from iCloud Drive?' Other times things are 'uploading'. Some things will open as zip files. I have no idea why? When we moved things to Drive, I saw all of these little clouds with download arrows.

Also, when we moved things to iCloud Drive, even though 'optimize storage' was unchecked, after it completed, the optimize storage box automatically, REchecked itself. It appears I had a good amount of space left, so I'm not sure if that's because it downloaded my Photos Library in reduced resolution so everything would fit?

Since I want my full resolution Photos Library, some stuff pixilated already from that 'optimize now' being checked repeatedly, would the following plan work?...

- Erase and reinstall.

- Check iCloud Drive and Photos ONLY.

- Download Photos Library, hoping it all fits and the 'optimize storage' box doesn't automatically recheck itself.

- Copy Photos Library to my 2 externals. Also, do a Time Machine backup. I have an external drive for Time Machine, as well. (I don't plan on adding to the Photos app ever again since resolution has been randomly reduced, maybe because I was deleting some originals, not realizing cloud would reduce resolution, or maybe because I just didn't have enough space.)

- After Photos Library copied to 2 externals and a time machine backup completes, do ANOTHER erase and reinstall, this time checking ONLY iCloud Drive and Desktop and Documents.

- Then UNCHECK all boxes and manage on my own from here on out. I realize anything NEW won't be saved in Cloud or Drive, but I want, at least, my current stuff saved up there. I'm not sure why some stuff is in Drive, some in Cloud?

Ultimately, I only want my Desktop and Documents stored on my computer. My Photos Library on 2 externals. Stumped as to how to do this, especially since some stuff is in Drive, some in Cloud, I'm assuming because some things want to download, some upload, and those zip files.

I'm about to start emailing myself every picture and document, thousands, only videos can't be emailed. I'm THAT frustrated.

Please help.

[Edited by Moderator]