I have a T14s Gen 3 with the middle tier 6 core CPU (forget the exact specs). But it's able to discipate about 30-40 watts (combined CPU and iGPU) in my testing which is more than enough for a "thin and light" laptop.

I can't speak for the newer T14 (full sized) but my T14 gen 1 intel has pretty weak cooling. The fan just isn't capable of spinning very fast which is nice for keeping the noise down, but it can't dissipate that much heat. Hopefully they've improved the cooling since then. There's no reason the slim model should be better than the full fat version in anything other than size, but who knows with Lenovo.

The P14s has a dual heatpipe, I imagine the T14 does as well. The T14s has a wider heatpipe than the single heatpipe Intel T14 models with integrated graphics.

I believe the T14 is tuned for faster fan speeds and longer bursts than the T14s, and the P14s even moreso. So if you want quiet, get the T14s, and if you want speed get the P14s.

The T14s has two USB4 ports, the T14 and P14s only have one.

I have a t14 gen 3 amd and thermals are great. I love how it has good airflow in from the button and out to the side.