Yes you can have them both connected.
Booting to which one can be determined by changing the BIOS setup option, boot priority.
Or you could use a boot manager, which will be aware of both OS's and give you the option of which to boot at start up.
The drawback of the BIOS boot priority, it's a slight inconvience.
The drawback of a boot manager, some configurations can be tricky to uninstall if you want to change your setup down the road.