Friend lagging crazily on minecraft, help

so my friend who has a awful pc got an upgrade to a better pc (better than mine actually) but for some odd reason, he still hit ~10 FPS on the lowest possible settings, hes using a 5070 so i dont know if that the issue, and the modpack we're playing on uses like 20 mods (most of them are optimization mods) and the really stange thing is when he plays on SKlauncher, it is completely fine, he can even play with shaders, but when he tries to play with curseforge, he gets like 7~FPS on some modpacks but others are fine?, even tha main menu lags?