It's weird with these types of guys, some people find themselves not knowing where he fits, other people have trouble imagining where he can't fit.
I think immediately Jaylen Samuels is the Dolphins' short yardage tailback, and their tight red zone tailback.
They've been experimenting with MarQueis Gray taking dive snaps from an upback position. That should have a role, particularly as Gray has been used as a lead blocker some. But I don't know that it's your primary option on a 2nd & 1, or a 3rd & 1, 3rd & 2; any carry that's a full yard to a yard and a half. Despite some good size, I also don't know that Kenyan Drake is ever going to be ideal in those situations.
As for tight red zone, that's where I think Jaylen Samuels could make a big difference. He's one of the most efficient goal-to-go tailbacks I've ever tracked, and part of it has to be because he's such a big receiving threat. It matters in those tight spaces that he's a threat to go run into the flat, or run out to the slot and catch the ball on a stick route or something.
Clearly at NC State they found success with him on jet sweeps and other outside runs, outside zone, etc. That's something Miami likes to do as well.
You could have a lot of synergy with both Jaylen Samuels and Jakeem Grant on the football field because the Dolphins like to experiment with Jakeem Grant coming out of the backfield, yet any personnel package that involves 3-WRs, one of which is Grant, and a Jaylen Samuels, is going to be ID'd as half-personnel, with whatever defensive packaging rules are in place for that game applying as such.
If you've got a formation shift with Samuels shifting out of the backfield into the slot, and Jakeem Grant shifting out of the slot into the backfield, there could be discrete matchup/defensive identification advantages to that. And since Samuels is so comfortable taking jet sweeps and running outside zone, and Jakeem Grant is a screaming bitch streaking out of the backfield to the perimeter, you could really create some Chip Kelly-like defensive dilemmas by stretching the defense on a polar axis.
Those are running advantages. That setup would have even stronger pass-based advantages.
Without even getting into novel personnel groupings though, it's pretty clear (to me) that Jaylen Samuels would be the best slot receiver option we have behind Jarvis Landry. Even if we keep Landry, injuries are not exactly uncommon in the NFL. The only true slot they have behind Landry is Leonte Carroo, and I don't find him to be trustworthy, especially with what they ask out of Landry which is to be powerful and elusive after the catch, after contact.
