Think about it this way.
Last season the Bills offense was actually relatively easy to defend from a schematic POV, because you only had to defend 30 yards of dirt at most regardless of down and distance. Without even an average deep threat else where, Gabe Davis struggled bigtime as the sole threat downfield, and defenses didn't really adjust a thing. They set either 2 or 1 safety 20 yards down field, one of them went deep, and everyone else sank down. Diggs wasn't that effective of a deep threat, and defenses felt they could run with him past 10-15 yards.
With the addition of Samuel, you inject pure speed with addition of being a real football player. It doesn't matter where he lines up, you can attack those safeties from inside or outside. But Samuel will only be PART of that solve.
The other part? Someone like Ladd McConkey who's the other deep threat. It allows for versatility. If you're on 1st and 10 or 2nd and medium, you have different packages that can make use of 1 or both deep guys, and you can use that short to intermediate offense that Allen proved he can run this past season. Defenses starting to squat? Well put in both speed guys, add in Diggs and Kincaid to the underneath, and you're either creating deeper mismatches, or forcing zones and YAC openings in the middle and short.
This is all about deployment of weapons. Bills can attack any down and distance and create matchups they like