magye Lets be real: google phones have underpowered chips for the same price compared to everyone else in the industry.
But Google devices are not underpowered when it comes to security, which is why the GrapheneOS project, which is focused on security and privacy, runs on Pixels.
magye My question is, how well do apps run on older pixels(5/6)
GrapheneOS support for the 5 series is over, because they can no longer be secured. The 6 series security is still fine. The expected schedule for Google's firmware end-of-life for various devices is here: https://endoflife.date/pixel
magye I hate when my phone lags or even shutters, or delays while loading apps. I want my phone to last me 3/4 years. Is it something that this setup can do if I buy pixel 9/10?
As of this time, GrapheneOS is not yet supported on the Pixel 10. It may well happen in the next few weeks. This is the list of devices supported by GrapheneOS.
Videos online of people using GrapheneOS might provide some confidence about performance. But the GrapheneOS project is focused on providing the most secure Android platform, not the most lag-free platform, and it's hard to know exactly what performance anybody requires, so it's hard to provide a guarantee that GrapheneOS will meet your performance needs.