i'm pretty sure it's explicitly stated that she has two powers. That her strength and durability are separate, but that her having both is what allows her to use the great degree of super strength that she has. Traditionally, you'd be right that super strength and super duribility would be one and the same power. But it's like how in some media immortality gets separated from invulnerability when typically invulnerability is part of immortality.
I'd say MC would copy both given how he copied both of Mrs Powell's powers. If MCs power is to copy powers I don't think the number would be the issue.
Again, I'm almost positive it was said that Mrs Powell actually has two powers, but they tend to work together as one. I'm pretty sure this was explained around the time we were told that there's no "flying" power. That everyone who can fly are using a different power in a way that allows them to fly. So Haper can fly by lifting herself with power, as can Reily. Someone who can manipulate gravity could fly by removing gravity for themselves as an example.
I'd say the artificial power can't be copied at all. The artificial power is a temporary power granted by the drug. The way I see it is that MCs power copies the parts of peoples DNA that grants them their powers and adds it to his own. The borrowed powers from the drug don't actually alter the useres DNA, otherwise Felicity wouldn't have the problem she does. She'd have taken the shot, and have the shapeshifting power forever. But she doesnt, and her body can't replicate the power. So, to me, ut makes sense that MC can't copy the fake powers, there's nothing there to copy. Darkvision is Felicity's own power, it's in her DNA so MC was able to copy it.
Also, and not aimed at you specifically, but it occured to me, that the reason MC has been able to copy some powers faster than others is the ones he copied pretty easily are the ones that are consstantly "on". So Mrs Powell's duribility and Felicity's darkvision, they're both pasive powers, not active powers like all the others. Lighting girl's powers have some passive aspect to them which is why they can copied pretty fast if not masterfully so. Like MC was passively "currupting" Artemisia with the energy power, it wasn't an acitve use of the power.
