Typically, your games 32-bit should be compatible with 64-bit systems, only that some restrictions exist, such as:
- Have a maximum (2GB) RAM allocation.
- Very small performance drop (compared to their 64-bit counterparts, but should be unnoticeable).
As for the "keep all my personal files and apps upon reinstall" bit, it will preserve your inner system information, such as the registry and user information, almost like an upgrade.
The "keep all my personal files upon reinstall" will however, not preserve your inner system information and instead just create an [unusable] copy of your old system in
C:\Windows.old\... and then install a fresh copy of Windows, which is like installing a new operating system (only that it keeps the old files; automatic backup)
See this SuperUser question for more information.