1st, you need to understand what is PF for ?
Layman term, it is
part of your main memory for the OS, and yes, it is hell a lot slower than your real memory.
Here how it works, once you run out of real memory, the OS will start to swap out "rarely" used part of the memory into the PF to free up some real memory. Ok, again have to admit its oversimplified, actually its more complex than that, but I think this is enough to give you some clue.
Mark the word "run out of real/main memory", for today rig with 1 or 2 Gig of ram and running average application, this is no biggie.
Here simple/easy example, imagine you're running a photo editing "simultanously" on 20 huge images with each about 200MB, then you will see your rig crawling like hell since it running out of real memory and the OS will start using the PF
as part of the memory, that process is called memory swapping or paging.
Your drive will work like hell when that happened, that is one of the reason the idea to put the PF on separate drive or fastest drive rather than main OS/program drive will help the overall performance.
Now about the page file fragmentation, in Windows OS, that PF file is sort of unique and exclusively locked by the OS. Try delete your pagefile.sys, you simply can't in normal mode, and it is just laid there
from the 1st time it was created or modified, so its not created "everytime" you boot the rig.
Thund3rball si right, only 3rd party defragger can defrag it or special OS mode like mentioned above.
That is why if that PF is heavily fragmented "AND" the rig does paging "heavily", it will surely impact the performance since the HD head needs to hop around to access it instead of single fragment contigous page file.
Regarding the size, for common usage, 1 to 1.5 times of memory is ok for "average" usage.
Since you understand what PF really is, now I bet you will say "Actually, It Really Depends !" or you could easily answer the OP question now.
Regarding setting the min equal to max, we just force the OS not to wildly extend it's size cause once your hard disk doesn't have single contigous space large enough for it, the OS will start to scatter that PF files around which is bad. But again, its not that simple, even you're not running out of main memory, Windows sometimes will just extend it, why ?, only Microsoft could answer that.
Hope this "oversimplied" explanation helps.