Exhaust pipe shape and flow

I've noticed some brit twins have nice rounded curved exhaust pipes, and some have a straight section that is near the angle of the down tube and has more abrupt curves near the head and silencer. Do they flow the same? What is the purpose for pipes with a straight section that is seemingly more compact and further away from the front tire?

If you look as some of the F! car exhausts from the past, with their convoluted curves and bends, I don't think it matters.
What does matter though is length. Phil Irving's "Tuning for Speed" discusses that very well. All to do with the sonic pulse at the opening valve travelling to the end of the pipe and back to maximise extraction of the next pulse.
Also, have a look at the exhaust of the Britten. All that curvy pipe is the achieve the "right" length: https://christchurchartgallery.org.nz/exhibitions/great-britten