I wouldn't because if everything around was to scale I'd think I'm normal

The expression "giant" is a relative one. It intrinsically compares size to average persons. When everything including people around you is to scale you are no giant.

...air/oxygen consumption..? Theres only a finite amount in our atmosphere at any given time after all.

Your atoms would still be the same size, so they'd be smaller relative to your new size, so your physiology would be inappropriate for your body proportions and you'd probably die, maybe quickly.

M’knee joints would give out

I presume there are physiological things that would cause health problems or even be fatal for giant humans (it was actually an article about why there can't be giant ants that I was reading for non-weird reasons)

If i assume that the earth was scaled by the same factor and has the same density as always I'd probably have massive backpain, as merely bigger bodyparts wouldn't make my body suitable for a higher gravitational force