Planned routes were:
North End
-Bury (Bury Interchange being a hangover of the plan)
-Bolton via Radcliffe
-As a later phase, Oldham/Rochdale
South End
-Hazel Grove (the electrification there also being a hangover of the plan)
-Alderley Edge via Stockport
-Wilmslow via Styal
-Manchester Airport
I think if it had happened, it would have left Manchester with a very good transport system that could have been gradually expanded, but clearly circumstances conspired against it happening, and something a bit more modest - at least initially - was needed.
When you think about it, Metrolink was visionary stuff when first proposed, and from modest beginnings it's gone on to become a comprehensive and very effective network. If Manchester were ever to need underground railways in the future, it could be done by building tunnel sections for Metrolink, as several German tram systems have done.
For those interested, the bus museum in Manchester contains a Picc-Vicc display and also the original T68 tram mockup, so it covers the history of these schemes pretty well. Worth a visit if you're in the area.