I'm finishing my attic. The eaves aren't ventilated nor is there a ridge vent. There's a thermostatic attic gable fan at one end. Once drywalled, air can circulate behind the knee wall, in the rafters (baffling), and in a boxed area around the gable fan. As I understand my options, I can either add some sort of vent in my roof to let hot air escape (and to intake air if fan is running) or convert some of my eaves to vents. Are these all my options?
I'm pretty handy, but my roof is steep enough that I'd have to hire that work out. I'd do the eaves myself. If converting the eaves to vents, Is it possible to just drill a series of holes in my eaves (and through the plywood behind it) instead of pulling the existing eave covers off and swapping them out? There are a generic vinyl type.

If you have baffles in each rafter, I would put on a ridge vent. Is there a small triangle with a flat ceiling for the air from the baffles to dump into, and out the ridge vent?
Do you have any wiring in the sloping side ceilings? Very easy to cook it with all the heat. That's another reason why a ridge vent is best.
(I personally am scared of wiring running through finished attics above knee walls. I have seen it crumble.)

Eaves - are you sure they are solid? Yes, regardless of an electric fan blowing air out from behind the kneewalls, that's not enough. You need air coming up through the eaves. Whatever you choose to do, make sure there is screening to keep bugs and small animals out. I'd take out one piece of vinyl under each rafter if installed the short way, and one long one if installed the long way, and replace with perforated vinyl.

There is a triangle space at the top of the rafters. The hope is that a gable fan will primarily pull from that triangle space, and the vacuum created will then pull up air through the baffling from the eaves.

Sounds good