X64 or x86 windows for older stuff?

use 64 bit, it still supports 32 bit applications anyways

64 Bit will not run 16 Bit programs, stick with 32 if you need to run old programs.

or you can always get a free DOS emulator

XP Mode in 7 or Virtual Box

Yeah, at this point I would get 64 bit, and look at other workarounds for compatibility problems. For your software, you can use DOSBox if you have really old 16 bit games, or continue to run Windows XP in a virtual machine with VMWare or Virtual Box. Windows XP mode also works if you have Windows 7 Professional or higher.

As for device drivers, if there are no 64 bit drivers available, you may be out of luck and will have to replace the affected devices. Unfortunately, for a lot of devices older than 2005, and even some devices newer than that, don't have 65 bit drivers. The manufacturers did not bother making 64 bit drivers for them. Your two options for them is either replace, or use a 32 bit OS and be restricted to 4GB of RAM maximum.

I have ALLOT of XP keys just sitting around of home edition and professional. I might get a larger 1TB hard drive and run both 32-bit and 64-bit on different partitions but I heard of some way to get around the memory limit on 32-bit somewhere.

There is no way to get around the 32 bit limit. You can use the LAA flag to make 32 bit applications use a maximum of 4GB of RAM, rather than a maximum of 2GB of RAM that is default.

There is also physical address extension, which XP 32 bit already uses by default, at least as of SP3, which does extend the addressing a bit to allow the full 4GB of RAM to be recognized by XP despite some addressing space being taken up by motherboard devices. It technically allows for more addressing than the 32 bit limit, but in practical terms, it won't let you use more than 4GB of RAM.

If you want to take full advantage of more than 4GB of RAM, you need a 64 bit operating system.

you can try to force the PAE when booting but there is no guarantee it will work.