Part of the difficulty may have also been because it was my first foray into Android... at the moment I don't have a specific example, but I seem to remember setting defaults was straight-forward; but either they were not always respected by certain interaction prompts, or some similar behavior.
As for GMail, I'm also no longer using the app and instead have opted for Spark (personal mailboxes) & Outlook (exchange, work)...
I've just recently switched from a Galaxy S10 to a Pixel 7 as I wanted to see the "vanilla" experience, as well as be closer to upstream for software updates. My S10 still works great, though the battery needs replacement (at the time, it had already broken the glue on the back glass and was still expanding -- didn't realize until I took it out of the case for cleaning)...
With my S10, I had to really fight to get it to let me use Google's apps over the Samsung ones; which whole annoying is doable. So far, the only things I really miss from Samsung (and notably the UX):
Overall, I'm happy with the experience so far; though I dunno if the "Pro" model of anything is really worth it.
May be worth building a default config to "install" for those setups; that's saved me quite some time when configuring new/spare machines at work.