I hope RAM2Sav is safe.
Then again, the only edits I'll make in PKHex are changing ID/SID, maybe Trainer Name, Battle Points, PokeMiles, Money (not necessary though), Items (especially not the Key Items nor the TMs/HMs part), Wondercards, and some visible stuff such as correctly adding mons in boxes.
I hope they won't modify other parts of the save.
So if there's something I don't understand, maybe it's safe not to tamper with it right? Example such as that "Stats" in the bottom right corner in the Trainer Info with things like 0x000