Troopers or "troopers"

Who exactly do the Rebel Captain and Hoth trooper Officer's commander effect's benefit? Is it just the characters named "Rebel Trooper", or "troopers" within the Rebel faction? What about the rebel heavey trooper?
I believe its any rebel with 'trooper' in the name. So that's a green light on the heavy trooper.
AMS-51 "Dendrite" Connection lost...searching...
Both. Check "Trooper" in the glossary in any recent rule book:
What if garm brought in a New republic trooper into a rebel squad? Would they benefit from the rebel captains CE?
All together now: Search (for "affinity") is our friend:

Yes.When you bring a character into a squad through Affinity, they are considered to be part of that faction.

For reference, this is covered in the rulebook glossary under Affinity.

It's not affinity it's reinforcements.
They would not as they are of the New Republic faction, and the Rebel Captain's CE only affects troopers of the Rebel Faction.