It's neither thermal or battery issues. My 10.5 Pro was perfectly smooth and fluid on 14.3 and is again smooth in the 14.5 beta. It was terrible on 14.4.It’s NOT the OS. It’s thermal or battery throttling. The OS is telling your battery and CPU the battery is toast. Slow down the CPU and GPU significantly. We can’t tell but you are most likely at best getting 50% or less of your Max Performance.