The experience is smooth, the software is well optimized for the hardware, but if you're looking for the top specs and are a big mobile gamer, I don't think you'd be happy.
For me, I don't game at all on my phone, so it's perfect for me. I love the user experience, the helpful AI features, and the photos Pixel's take. I picked up the 8 Pro and it feels a lot more refined and uncompromising in almost all the ways.
RCS is just a standard, much like how SMS is just a standard. Google's Messaging app is just one implementation of it, though it probably is the most popular in the US it is not the only one, nor is Google able to decide who cannot use it. Carriers typically have their own, though you may have recently heard that T-Mobile decided to switch over to Google's.
Pyenv! Let the OS have its own version and work on whatever version you want, whenever.
Probably an unpopular opinion on here, but the OS I recommend for grandparents and parents is ChromeOS. It's so locked down that it's almost indestructible, and they almost never need any specialized software that you'd use Windows/MacOS for. If you're savvy enough you can also use Linux on it in a container, which is how I prefer to use it for day to day stuff (in my case, data related workflows).
I picked up the 8pro. The fingerprint reader is fine, maybe marginally improved over the 7pro. It's nowhere near the ultrasonic fingerprint readers. But, it now has Class 3 secure face unlock, which is good enough for banking and other apps, and combined with the fingerprint reader, it's pretty quick to unlock.