Can you play with 1 GM and 1 player (the player controling around 4 characters)?
Can you play with 1 GM and 1 player?
Wow!
Yes, you can, but I imagine it will be a challenge for the player to control so many characters, as the game is full of parts to take care of.
I would suggest the PC starting with 2 characters and maybe getting a third as he/she understand better the mechanics. Also, the adventures released so far aim for a group of three characters.
Also, if it was me, I would run a "GM's PC", a character that, even though is a NPC, is part of the group. That because it would give to the player the chance to interact with a character played by another person.
It could be done. Honestly, though, I'd just suggest having the player use a single character and the GM run adventures suitable for that single character. Occasionally, the GM can provide NPCs as support if needed, but I think it would work best as a single-character adventure.