Summary
It is possible to install multiple scan engines on the same workstation. However, there is no user interface to toggle between them.
Workaround
Edit the LF.ini to select which scanning engine to use.
ScanEngine=LFWISISN.exe
ScanEngine=LFKOFAX.exe
ScanEngine=LFTWAIN.exe
ScanEngine=LFUNVCPT.dll
More Information
See the following article for information on where to locate the LF.ini file for your operating system:
100162 Finding the LF.ini File.