Yeah. Performance might not be a huge deal, but even for simple games like a platformer, any sort of lag/delay could make the controls feel pretty bad. Maybe dev in a VM, but frequently test builds of the game outside. The dual boot is a pretty attractive option. I might do that since I probably don't need that many "instances". (Or perhaps have multiple drives that I swap physically. Not the best, but that way I don't have to deal with boot loaders/managers. One main drive, and another just to mess around. One that I can format easily.)VMs would ensure no conflicts between different installations. But they also run slower, since you'd be running two OS's simultaneously. If performance is a big deal for your coding experiments I wouldn't do it unless your PC is a beast or your programs aren't performance-heavy anyway.
Another option is to dual boot two different OS installations on different partitions of your hard drive. You would have two Windows on the same computer, not interacting with each other, basically.
Visual Studio 2015 comes with C++ toolsets for VS2013 and VS2012. The Windows 7.1 SDK comes with VS2010 and VS2008 toolsets. So if you're only keeping the old versions of Visual Studio installed for older C++ projects in theory only need to install Visual Studio 2015 along with the Windows 7.1 SDK to have access to all the compilers from Visual Studio 2008 onward.
Good to know! Thanks!