Personally, I would trust Violet from Violet. She would never forget to warn you of upcoming hazards and wouldn’t walk you into things by accident. I would never trust Grunk from Lost Pig.
Edit: Phoebe from Blue Lacuna would be pretty solid because she seems quite reasonable. Another person I would never ever want though is master Bryce.
Good question. I can tell you one thing. It certainly wouldn’t be Igor from Igor’s Quest, probably for much the same reason that you singled out Grunk. However, they are both PCs, not NPCs. Does that matter?
No, play a character still count. The thing is, I think Grunk would be very well meaning but would be total chaos. I can’t remember whether I mentioned in my original post but I think Alex from counterfeit monkey might not be a bad guide, since that is essentially what he is doing during the game, but giving info rather than actual physical guiding.