I've been trying to analyze how many PCs still use 32 bit OS now, and found only one clue, that 56% of Windows 7 installations (in some unspecified year) were 32 bit.
I'm having a hard time believing that was ever true - if I remember correctly, 64-bit started becoming the more common version since Windows 7 (or possibly Vista). Maybe I'm wrong, but even so, this seems very out of date.
Steam hardware survey for Windows shows 8.42% for 32-bit, 91.49% for 64-bit (0.09% unknown). It may be that the 32-bit levels for people interested in either Open Source games or casual games may be higher, but I'd be surprised if it's that much higher. (I'm also not convinced Linux is that much better - for example, Ubuntu until 13.04 were still recommending people download the 32-bit version -
https://www.howtogeek.com/165144/htg-ex ... ntu-linux/ - though people on Ubuntu may well have upgraded enough such that that doesn't matter now.)
Having said that, unless your game benefits from 64-bit, you might as well stick with 32-bit, which runs fine on 64-bit Windows, and not bother about two versions. I've always done 32-bit for Windows (especially as the Express versions of Visual Studio have traditionally only supported 32-bit - though this may no longer be the case, especially with the new Community Edition versions).
But then, if you need 6-8GB RAM, I don't see how that's going to be possible on 32-bit systems anyway...