I cannot help you with "CaptureOnTouch Pro" specifically, but to answer your question, no you don't need and shouldn't be using both USB redirection and Scanner redirection at the same time for the same device.  Generally, avoid USB redirection whenever there is a built virtual channel as there is for scanner, serial, etc...  It's a great idea to blanket deny all USB and then only allow approved devices by PIDs to avoid inadvertent devices into your sessions. 

your coworker is right, scanning *should* work via scanner redirection provided there are compatible WIA or TWAIN drivers.  You should see the redirected device in the scanning app in your session system tray.  With scanner redirection the application only sees the generic device  " VMware Virtual WIA Scanner imaging device"   It might also say TWAIN if that's your driver type.  When in doubt, verify with another application.  If there is a TWAIN driver install that use TWACKER to verify driver compliance on the endpoint.  e.g if twacker doesn't work on the endpoint 100% it won't work in the session either.