[Google Pixel 3a XL Questions & Answers] krabman:
It's relevant. I'm not sure where you started but it tells you your going to need the full image. It can be flashed irregardless of whether debugging is enabled, the phones lock status, and will partition. Going back to the beginning those times I told you were not made up, if you're familiar with this stuff you can go through it very quickly. Less so and it takes a little more time but it's still not terrible. Up front, I'm not a guru, you know that but I'm telling you that because I'm not claiming such, only that I do have a lot of experience with this which really just means I've made more mistakes and tried to profit from the associated beatings. I'd also say that as long as you can get in fastboot the phone is very seldom going to have to go back, you just need to flash a factory image but to do that you have to create a working environment. So... Here is what I would suggest based on what you've posted so far.

I'd delete every image you downloaded, go to Googs official site and download either the latest Pie, or 10 (Q) depending on which way you want to go. You're doing this because you don't want to have stacking problems that would both prevent a successful flash because it makes it much harder to sort out your problems. So get rid of what you got, go to Googles site and get the correct full image. At the very least you should verify the size match but the recommended procedure is to check the MD5. You will also want to go get the latest platform tools and for the same reasons. Both of these are linked in the link I left for you showing how to get out of a soft-brick. The link will be your next step: go there and familiarize yourself with the entire process. I'm not talking about studying for an exam, you just want to have an idea of what your about and the general procedure you're going to follow. That link is for an 3XL but the steps are all valid here just keep in mind when you go to Google's site to get the image, make sure it's the 3aXL.

So you've got the latest tools and a solid image; these should be good to go but you'll have to decide what portion of all those procedures you want to follow to completion. This is going to be based on experience. Mine tells me if you got as far as you did your drivers are probably good and I would skip that. I'd have on hand at least 2 A to C USB cables. As long as they're decent quality cables one will probably work. Ports on a desktop PC will usually be divided by the front and the back, one being on a hub, the other direct so usually trying once in the front and once in the back is going to get you on a working port. A laptop is more of a crapshoot. If you have them on both sides you'll be wanting to try one on each side but the port is far less likely to be a problem than the cable and usually you cant see your device if one isn't going to work for you so I'd worry about trying those last.

At this point you're ready to follow the procedure as described on that link for setting up the tools and flashing the rom. If it works you're done, if not try switching cables. If that fails swap to the back of your desktop and try both cables again. With a laptop you'll try a port from one side with both cables and then the other, or the back depending on how your ports are laid out.

Chances are pretty good you're up and running at that point so go ahead and give that a go.