It basically comes down to this:
If it has a CC value, it can CC.
If it has a FF value, it can FF.
That´s the only thing that matters. Well, and having a LoS in the case of FF.
And yes, a formation of Dark Reapers is quite excellent as support!

Edit: To add a rulebook quote, as one should when answering rules questions:
1.12.5 Resolve Attacks
...
Units have two assault values: a close combat value and a
firefight value. Units that are in base-to-base contact with
the enemy must use their close combat value, while units
that are not in base contact but are within 15cm and have
a line of fire to an enemy unit can use their firefight
value.
...
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