It doesn’t matter what the seat is in (fairing, cargo bay, service bay, etc.), the kerbal always causes drag even though no parts inside with it (including the seat) cause any drag. The drag caused by kerbals isn’t too bad when they are seated vertically, but if you lay them down, it increases by nearly 10x. Basically the bug is that kerbals in command seats (but not the seat itself) cause drag no matter where the seat is, even if it should be shielded by something.
And I don’t have any mods. I’m not going into EVA from inside the fairing. I’m coming from outside the fairing, clipping the camera into it to see the command seat, then getting close enough to board. The kerbal basically just teleports through the fairing. But the only thing that would keep you from being able to EVA from inside a fairing is if the fairing wall is too close to the crew hatch. Also, if you EVA from a command seat from inside the fairing, you just get shoved out of the fairing.