Installing another OS onto the phone is not impossible, but can be tricky. I could write out a guide for you on how to do it, but fair warning, can be tedious and does require a bit of knowledge on sideloading an OS onto it.
If you are not willing or able to do this process, my recommendation would be to get a Pixel 3A or 4A, which has the basics of a Pixel for a more affordable price. I’d stay more with a 3A for now because again, is more affordable, and will continue on receiving updates for at least two years I believe. If you want the full experience of a Pixel, then either the 3 or 4 would be your best bet.
The Pixel 4 is a bit more right now, as is the newest addition to the line. The Pixel 3 retains some of the most beloved features of the previous Pixels. Unlimited Photo Storage on Google Photos, prerelease of Beta software and more.
Any questions, let me know.
Alex H.