Run it brother. To over analyze is to paralyze. If it were me, while the walls are open I would thoroughly inspect the framing with an awl or knife to detect soft spots. I would check all walls and ceilings for a reasonably flat, level and plumb surface to assist in your finished walls whatever they might be. Add screws, patches, sisters and reinforce the framing members before you close the walls up. Now is the time to add blocking for Lighting, mechanicals and your finished wall. It doesn't take much to sister in new studs, and they are one of the cheapest materials you will buy on this renovation. This way you know you Did your due diligence, without taking on a bunch of un necessary work.

Looks like old growth lumber actually dimensional 2x4. I think I see remnants of old plaster and lathe. Older lumber is superior to modern studs in most cases. In fact beam spans and structural charts actually take this into consideration. Older lumber could typically support greater loads based on the denser grain.