Question – LineageOS 24 (17) VS PixelOS (17)

LineageOS means no GApps by default, you need to flash them separately (of course if you want them, for me lack of GApps is a feature), and it’s just (mostly) pure AOSP only with little improvements/added features (like ability to revoke internet permission for particular app) and no UI tweaks except basic launcher customization. For some reason new Android versions are delayed if you use official releases, unofficial builds don’t have such problems. I prefer this one because of no GApps (I don’t need integrity so MicroG is enough).
PixelOS is just some Pixel-like ROM, haven’t tested it so far, it has some customization features and GApps ootb. It may be less stable than LineageOS but you need to test yourself. When I tried EvoX (another Pixel ROM) on some device stability was a problem.