In a project everything must be prepared.
1. The team is experienced in technology so their concept will be good if it is experienced.
In fact, everything on your list is important for the successful development of a new project. However, if I have to choose one thing, then of course i will choose the first item. For investors, it is much more important that project developers have successful experience in creating other projects. It is in such projects that they most successfully invest and as a result get a good profit.