Using Cubase AI5 as a VST controller live


Can AI5 ve used as a ‘live’ controller? I play in a band, and whilst I use a MOX6 and a PX3 Privia for sounds, I can use a MIDI controller for extra sounds, so i have some soft synths downloaded. Is there only 2 VST instruments I can use? For example, if i used a sound on track 1 for one song, then wanted to switch to another channel for another sound…Also, do i need to click on the synths to change the sounds, or MIDI channels on the keyboard…As you can tell, I’m a novice when it comes to MIDI/Soft Synths etc…!!

Thanks in advance for any help!!