Team Playbook - Question about Allies and Enemies

I'm running a campaign right now and my players are using one of the Team Playbooks from Codex of Worlds. I'm curious how exactly to use the Allies and Enemies. It has you pick up front when you pick your moves and assets. But the playgroup decided to figure it out as we went. It felt especially early to pick your Enemy.

My plan was to introduce NPCs and Badguys along the way, and see if my players liked or developed relationships/rivalries with them. But after the first session I realized I would have to shoehorn in an NPC to a session for that to work. Plus I would have to introduce that character as someone that the PCs already know, otherwise whose to say they would know they could be an Ally? So at that point I might as well have developed them together with the players?

As for Enemies, are they meant to be known to the PCs already? I was picturing them as the big bad's of a campaigns Arc which you would maybe want to keep a secret till latter sessions. But maybe that's not the same role? Are Enemies meant to be more of a obstacle than the Arch Nemesis?

I'll probably broach the subject with my players and try and come up with something together. But I was curious what others experience has been.