[Pixel C General] locuturus:
I am not aware of better or worse serial numbers. I assume later is better? Mine has image retention / ghosting & a purple shift in white balance but I never got the half screen failure or other issues.

I recommend either Pixel Experience 10 or LineageOS 17 if you are at all comfortable with flashing. ROMs are little more work. But they offer the latest patches, some new features, some specific fixes for our aging hardware, and because you have to install TWRP first you have that safety net for when things go wrong. I also happen to really like Android 10 for what that's worth. You might have to use Magisk Hide to get some apps working, and you probably have to sideload Netflix from APKmirror but it should work just fine.

If you don't mind how it works out of the box, and you don't care for fiddling with it, and you aren't concerned with the screen lock bug, then stock is perfectly fine. Some people say 7 was better than 8 because of some video driver bug that broke a few Unity based games. I have zero idea if this was fixed in any of the ROMs.

I am considering selling my Galaxy Tab S6, even though it is nicer in so many ways, because I just disagree with so many Samsung UX decisions. So I continue to use the Pixel C and I hope you like yours. I am a little envious you found a good condition 64GB one! There are countless little touches where the Pixel C does what I expect and my Samsung devices do not. Using an USB audio device? Pixel C can use it for music and also to make VoIP calls. Believe it or not many Samsungs cannot route 'phone' type audio over USB. Music only! Using a mouse? Open Chrome, right-click on a link. Notice that beautiful options menu that pops up? Try the same thing on a Samsung and notice it is just Android back function. Back to the Pixel C, try to middle-click on a link and notice it opens in a new tab in the background. Just like on desktop Chrome! Then, try with a Samsung and notice middle-click is the same as Android home function. Samsung just decided to break mousing and I hate it. Even things like display scaling work well on the Pixel C and badly on Samsung devices. Want everything to be very small? That's easy to do, and basically everything scales (except the nav bar, but there is a fix for that). On my Samsungs some parts of the UI scale and other parts don't. You end with comically unmatched icons and other elements like the notification shade. I really thought DeX could fix these issues for me and it didn't, but that is a different story. I like Samsung features but by golly they suck at the basics IMO.

Not everything in Google-land is good. The Pixel C was never trouble free and still isn't with even the best ROMs. 3GB of RAM was too little for a 'productivity device' in 2015 and obviously still isn't enough (your use-case should be fine however). The storage speed is slow, it is prone to occassional jank (probably combination slow storage & low RAM), and if the battery isn't perfectly healthy you will experience bad CPU throttling (this is fixed in ROMs and in my case was a night and day difference). You are already aware of the screen problems. The headphone jack quality is not good, and the bluetooth range for headsets is about 5 ft (I am not joking, it's astonishingly bad!). There used to be many WiFi reception complaints but I think it was fixed long ago. Reception is on the weak end however. The touch screen is sensitive to interference and you can get ghost touches when using a low quality charger (YMMV on that one, my hardware might be faulty). Last thing that comes to mind is that occassionally, and seemingly randomly, your lock screen PIN will just... stop working. If you are on stock software with a locked bootloader then all you can do is factory reset!! This alone is a great reason to go with ROMs.

Good luck and welcome to the community!