I don't know if you can use a Video Toaster 4000 card in an expanded A1200 but apart from that it just depends on how far you want to take things. For a while it was easier to find a cheap PCMCIA network card for the A1200 than a network adapter for an A4000 but that was a long time ago.
Yes you can use a video toaster on a zorro busboard on the a1200, as long as you had the video slot enabler
