overheating and shutting down could be bad if you are in the process of installing/editing the system content, like IOS or cIOS install, wad install, console updating (thought, now it's done so you are fine), Even savegame writing from a game.
It could corrupt your file system, or even prevent the console from booting. it depends when that shutdown happens and what you were doing at that time.
If you installed all the softmod and don't need to touch the system content anymore, you are fine. the only issue you could encounter is in case the console shutdown while a game is writing its savegame. at best that savegame will be corrupted, at worst it could affect other files.
Maybe you could use USB Loaders setting to redirect all savegames to your external device, so instead of saving on the console it will use the SD or USB instead.
Do you ever use DVD on Wii too, or don't need any Disc form?
If you want to take advantage of the modchip, you might need system menu 4.1, as nintendo patched modchip region free in 4.2
But if you play all games from USB Loaders, then you don't have to worry about your system version. 4.3 is good for everything.
if you even intend to go back to 4.1, ask here first as it could be dangerous to install things manually without checking all your required files.
