I would say it's worth it, as long as you're sure that you're getting one that's in good condition and allows unlocking the bootloader, i.e. not a Verizon model or other that has the bootloader permanently locked. It's still a really good phone.
1. I've had no problems with heat. I have mine in a silicone case and can run demanding games and apps without it overheating, though it does get pretty warm to the touch.
2. As long as you have a version that allows unlocking the bootloader, rooting is pretty easy by following
this guide (though you'll need
this version of the safetynet fix), and bypassing SafetyNet/Play Integrity API while rooted works as well as on any other phone - it can't pass hardware attestation, but it can force basic and that's enough for most apps.
Do note that there is no TWRP for the Pixel 6 yet, but
PixelFlasher makes updating and Magisk patching very easy.