if you want to get rid of sidewall you should stretch tires. pumping up the tires is also bad for the tires if you drift on them. some tires will belt and chunk at higher psi like my federal 595s. i find running a low psi like 28psi is good because you have to account for heat temperatures of the track. that significantly heats up the tires and takes a toll on the tires.
if sidewall flex is a issue, get better tires or stretch them to reduce sidewall flex. if you run 55 sidewall or higher, you can’t expect much from them.
running higher psi is like pumping them to a balloon. you make less grip and if you use crappy tires, it significantly reduces grip.
i say just run crappy tires to begin with if you are a beginner, but pump them to normal pressures. drifting is about grip, and when you need the grip its there.
just my 2cents
PS: pumping tires more than 40psi COLD is actually reducing the surface area of the tires. having low pressure increases surface area and hence the better grip at lower pressures.