The general case for me has always been - If youre playing alone - do whatever you want with the game. Mod it, cheat id, eat it for breakfast - as long as you are having fun, nobody else should care.
Only whenever you venture into the multiplayer world (and that includes things like speedruns) should you be on an even playing ground.
Of course. I totally agree with that. Never use cheats when playing the same game with others. It just makes it completely unfair.