No matter what the initial reason for implementing the pagefile system was, pagefiles are still used, even heavily used by Windows today as nowadays available software has developed as well, not only available RAM, and are much more demanding today than they were back in the days when there's much less RAM available.
Especially on gaming PCs there are programs running which need a lots of your installed RAM to perform properly, but also video post processings, packing/unpacking, streaming and such processes ... at worst all at once, require a place for Windows to swap data which are not urgently needed at the moment but will be needed later again. And that's what the pagefile is for.
Always let Windows manage this file/those files, unless you're absolutely sure what you're doing and know how large it should be (btw, Windows already recommends how large it should be). To prevent unnecessary fragmentation and HDD activity you can set a fixed size by setting the same value for min and max size. This way it won't be shrinked and then increased again depending on the workload. But to set the correct sizes you have to have a proper understanding of what Windows is doing with it and when.
The old 1.5 times your RAM rule still seems to hold true, as this is always Windows' own recommended pagefile size. So, for a 16 GB RAM machine it would be something about 24 GB pagefile size (recommended).
I don't know if it is useful or maybe even bad to have several pagefiles, I for one have a fixed size of 2 GB min/max on my boot drive (HDD) for partition C and a managed one on an SSD. But I was searching for pros and/or cons to have more than one pagefile or not, as I tend to delete the 2 GB on my boot partition. Alas, haven't found any valuable arguments yet, but I assume, just for the crash dump files and stuff, it's useful to allocate some GB for Windows' where the pagefile resides normally by default. Hence I leave it like that. But for the other SSDs where my games are installed I do not have any pagefile. Wouldn't even know which size they should have to make a difference, whereas I also don't want Windows to occupy another up to 24 GB on each SSD (or at least 16+ GB as it uses now for the managed pagefile).
'don't bother, ram is cheap' is a common reply which I find limited to a minimal user's perception. The idea is using any given hardware with optimal performance. The memory requirement depends on the user, and the 'cheap' depends on their budget. One may need an amount of memory which is not possible to install or buy. – SuperDuck – 2011-01-17T00:54:40.810