Not quite sure what scenario you have in mind, but FWIW, Sharpcap does not need a separate Astrotortilla installation to perform a Polar Alignmnent.
If you're talking about using Sharpcap to do a plate solve on your imaging target through your guidescope and then use something else to run a different camera (say, BackyardWhatever and a DSLR...) through your imaging scope, that would not likely be a good idea. I think you'd want to do the plate solve on what the *imaging* camera sees.
The whole point of plate solving is to get your target centered quickly and reliably in the field of view of your imaging camera. Your guiding FOV and your imaging FOV are unlikely to be the same, let alone precisely aligned. If you are using a control program of some kind for your imaging camera, the thing to do is get Astrotortilla (or equivalent) integrated with THAT.
I use BackYard Nikon with mine, integrated with Astrotortilla, and plate solving really is magic. :-)
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras: Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer: Thinkpad x230, Win7Pro/64