so if i understood your questions, you are asking what would be the bandwidth requirement for case 1, 2, 3.
what is not clear, is that are you using multiway or multisite? with multisite you can support 3 more participants to setup a conference. So for your case of having 5 participants you need MCU.
VC connection with 512 kb upload and 512 download, you need N x 512kb +10% overhead connection for MCU (where N is the number VC).
Anyway you need to provide a network diagram to show how your network infrastructure is laid out.
regards, Ahmad