Look at the main CB rating for each phase. You want a clamp at least that big. Not much bigger as this will reduce your resolution.
Unless… you know the CB is oversized for your loads. Then pick a lower rated CT for better resolution.
e.g. I have a 100A main circuit breaker, however I know I never get close to drawing that. So a 50A CT is ok. I’m not in the US but the same applies everywhere. How do you know this without measuring first? Look at the compliance plates for the major loads in your house (electric stove, Aircon etc…) and add them up.
Unless you have residual current CBs. Then the N must go to the same breaker as L (not the neutral bus), or you will get an unbalanced current that trips the breaker.
I’ve recently switched over from using mqtt to the Home Assistant integration. It works very well and is much easier to set up. There’s no need to use mqtt (or flash alternate firmware) for Shelly devices any more. The integration has come a long way. Very impressed.