For number collecting, Cambridge, Ipswich and Norwich are the three main hubs. All the branches are interesting in different ways, but you won’t see anything extra that you wouldn’t see at those three places, apart from the rather unusual collection of old rolling stock now gathered at Great Yarmouth.
Crown Point is your main problem. While the better view is from the Ipswich / Ely direction, a few units are stabled around the side of the shed which would be difficult to get the numbers of, and the view of some could be blocked by other units. Plus those inside the shed of course. Be aware there are four new sidings at Trowse on the down side of the Ipswich - Norwich line that may have 745s stabled.
The diagrams can be followed using the platform numbers in real time trains (but beware of on the day swaps). Most class 755 workings are simply out and back but Lowestoft is one place where sometimes the Norwich and Ipswich services swap over to keep the units within fuel range.