They’d both move around but Diggs and Hopkins can both be lethal in the slot. And we already know Allen can pick apart defenses with a capable slot. Diggs would catch 130 balls in the slot. Automatic.
The Bills went into last year wanting a veteran slot. Crowder was injured all year and Beane used that as an excuse for why McKenzie played so much. It wasn’t the plan.
I can’t see the plan being Harty, Shakir, and Sherfield. So I do see them adding a veteran slot WR, or maybe the plan is Diggs and add a premium WR that can play outside/inside.