If they resign DRob which I think is the most prudent move, than I think they've got a starting three there (Not saying it's a good starting three!) in Nacua, DRob and Whitt. I'm not sure they sign a WR after that but look to fill things out with two pass catchers in the draft.
The TE class is strong, I imagine one is coming from there and most likely a WR at some point. In this scenario, I suspect our 12 personnel to go through the roof and we slightly move away from an "everything looks the same" offense which we began to do last year some. I suspect our offense will look a bit more like the 49ers offense last three years in general.
And yeah, there's a scenario where Tutu comes back but I think it's unlikely. I think he'll get a modest contract somewhere else. Possibly with connections to LA. ATL maybe.