Asus Zenfone 10 is obviously the best choice physically speaking, since it’s I think the smallest high-end phone you can find. But in terms of updates, in my experience with a previous Asus phone (Zenfone Max Pro M2, bought it in 2020, was awesome back then but right now it’s just crap with non-stop random reboots, so I’m merely using it for 2FA now), it’s not so great. Maybe they changed since then, but even now they offer you only two major Android updates until 2025, and security updates until 2027.
Software updates are underrated and are the main deciding factor on when your phone is going to be obsoleted. I’d look for a Pixel (the 7a is a good fit for what you’re asking) or a Samsung instead, as both are quite generous with Android updates. I lean heavily towards Pixel phones because they have better support for custom ROMs (and also because I own a 7a).