The confusion and the reason you got modded down is that people don't understand that the segmentation is still present in the CPU, but that common practice now is to overlay all segments as a single 4GB space.
In other words, if you really really insisted you could mess around with giving the segment registers different base values and / or lengths but you'd probably end up regretting it.
You used to need them (badly), especially on the smaller CPUs because otherwise you were severely limited in memory.
Check out the 'mixed models' that were pretty common usage in the 80's.
There were lots of them:
code data model name
under 64KB under 64KB Small (-ms) or Tiny (-mt)
over 64KB under 64KB Medium (-mm)
under 64KB over 64KB Compact (-mc)
over 64KB over 64KB Large (-ml)
I was so happy when I finally got out of 'model hell' and could use 'flat' mode using DJGPP. Finally C programming without the headaches.
You're going to see a lot of references to segment selectors, and apart from the fact that FS may refer to thread information, you're never going to have to remember what any of it means. You can safely consider segmentation to be detritus.
In other words, if you really really insisted you could mess around with giving the segment registers different base values and / or lengths but you'd probably end up regretting it.