…as promised, here’s THE [VERY] LONG VERSION:
I’m brand new to the forum, and very nearly brand new to Audacity. Please indulge me a brief “stage setting” introduction:
I’'ve had some very limited experience in Audacity helping family members with music production for their projects and businesses, but to date, all my own work on my podcast, and what very little music production I sporadically do for myself has been pretty much entirely done in GarageBand. I’m working on gradually migrating away from macOS and Windows 10 to Linux (the “slow road” approach, not the “jump off a cliff” kind), and that means migrating away from GarageBand as well, which is the only DAW I am truly comfortable with.
After a bit of reading, it sounds like the ticket is to make the distinction between “sound recorder / editor” (i.e. creating and manipulating individual sound files), and “workstation” (i.e. putting all the sound files together into a final project.) Based on what I’ve read (and corroborated by my own experience), Audacity is EXCELLENT for the former, and passably useable as, but not at all strong as the latter, whereas GarageBand is the exact opposite, minimally capable as a recorder / editor, but excellent as a workstation. So, my plan is to start using Audacity as my recorder/editor, but use a different program for workstation. For the moment, I’ll keep using GarageBand for that purpose until I can find a program that works across mac, Windows, and most importantly, Linux that I can replace it with (a cursory reading makes me think LMMC will be a likely candidate, but I am WIDE OPEN for suggestions, even if they’re not free).
One other thing that will help me in this transition will be to “untether me” from the basement studio. As I said, right now, all my own production happens in GarageBand, which, obviously, means that all my production happens on my mac, which is tucked away in a basement studio. Not only does the basement studio leave me feeling cut off from the rest of the world, but it would also give me a lot more freedom, flexibility, and time to work on my production if I could share my work between my “podcasting mac” in the basement, my “gaming [Win10] PC” upstairs, and my cheapie Chromebook, or *buntu laptop abroad (or on friends and family’s equipment when I’m over at their houses). Obviously, using GarageBand, I can’t do this except for with friends and family who also have macs.
I’m presently working on a blooper reel for an episode of the podcast (for a mini-series on the music of the PC Engine / Turbografx16 that I did with a guest collaborator who is a TG16 podcaster), and I thought “why don’t I use this as a great chance to get started with Audacity?” So, I got all the source files put together in Audacity on my mac, and then tried, for the first time, to share a .aup file with the PC upstairs. At first the file would not open at all, but I was able to relatively quickly figure out that it was because Audacity created a folder to go along with the .aup file and I did not upload that to OneDrive to send to the PC. However, when I tried to upload a folder that was 3.1GB on the mac, OneDrive only uploaded 1.99GB of it, and thus, only 1.99GB of the data made it to the PC. And of course, when I tried opening the file, much of my audio was missing.
After reading the FAQ in the manual, I did read ideas like creating a .zip file, which is a good idea, or even to save a compressed version of the project and use that instead. Only it comes right out and says that’s lossy, and I don’t know how much. I think that going the .zip approach is probably the better option - at least to try first. 
But is there a better way to share .aup files? Even if I am successful in sharing projects between devices (which, again, on my first try, I was not), it is a cumbersome approach indeed to upload xyz to OneDrive, download it onto the destination device, open it, make changes, save changes, replace the old xyz with the new xyz on OneDrive, download the amended file on the new destination device, lather, rinse, repeat? Even if I do use a .zip file, or do the compress (.ogg?) file approach, that is still super cumbersome, and frought with the chance of getting my wires crossed.
Anyway, I heartily welcome your feedback, and assistance!
Cheers!