...so is parkour basically stunts or is it actually energy-efficient? there seem to be a lot of flips

a superhero with super-strength can afford to show off but is it designed to spend energy freely or balance speed/safety with energy output so you can actually breathe or fight at the end

(or is that just all in the preliminary cardio regimen)

It seems to largely depend on the individual traceur

Some focus on economy of energy and motion, some focus on showmanship

hmmmmmm. That makes sense, since it's not one of the super-formalized rules-heavy sports.

(also, 'traceur' is a cool word!)

Isn't it?

There's two different schools of approach, yeah, and some people focus on economy and others on the acrobatics