What exactly does enabling Lenovo Custom TDP Mode in SimpleDeckyTDP do? I've tested and not seeing much of a difference, as Legion + Y seems to allow me to switch TDP modes with STAPM on and I can also use the sliders to adjust TDP per game in the Steam UI.
That's what just had happened to me because i usually keep my Legion Go in balanced mode (white led) while just using it as desktop. In desktop mode to play Overwatch 2 and Doom Eternal i switch it to performance mode (red led) and custom (purple led) for the Baldur's Gate 3
However when i use it in handheld mode, i keep it in balanced (white led) and use SimpleDeckyTDP to change the TPD to the one that will last a little bit and give best performence and battery life