|I couldn't get an unblurry shot will all 3 units.. so we'll do this piecemeal.|
The Mounted Scouts for Kingdoms of Men has three drastically different weapon options: Bows (24"), Pistols (12" and Piercing 1) and Carbines (18" Piercing 1), what you pick decide to roll with has a big impact on how you use them.
Scouts with Pistols 100 Points
Barring terrible positioning, cavalry will always be able to retaliate against the pistol wielding scouts. Against speedier lists (like, Elves or Ratkin) the Scouts will likely be also threatened by any infantry they themselves can threaten. Against armies with average speed (like other KoM), you only have an inch or two to play with where you can shoot without being charged by enemy infantry. Against slow lists (Dwarves, or Undead with all that Shambling), but that's a pretty situational match up.
The point I'm trying to make is that the short range of the pistols really limits the options for this unit, and any Scouts with Pistols will probably die after firing their first volley.
The best uses for Scouts with Pistols seem to be:
-Chaff for your cavalry, just be able to stand in front of your Knights and take that hit. Being cavalry as well, they can keep pace with the Knights depending on how threatening you want to be. If you play it smart, they might even get to shoot before they die.
-Gunline protection. These could sit back while your ranged units and war machines lob death at the enemy. Should anything approach the gun line, the Pistol Scouts can canter up, get in the way of your enemy, and shoot... as can the rest of your gun line. After a turn of focused fire, the threat is hopefully removed, and if not, their only viable charge target should be the Scouts.
Scouts with Carbines 115 Points
The 15 point Carbine upgrade gives you an extra 6" for range versus the Pistols. At 18" away, you're still vulnerable to enemy cavalry, but should be able to safely shoot at enemy infantry for a turn or two, and the Piercing can help you actually whittle away a bit of your target.
You can still use Scouts with Carbines as chaff or for gun line protection, but the extra range means fewer threats for them and a better chance to survive, and therefore more options.
I've really liked these in combined-arms lists. Stick them with infantry. The Infantry can move quickly and the Scouts can keep pace while shooting. They can also screen the infantry from enemy fire while everyone advances. These Scouts are really useful... but unlikely to stick around for long.
Scouts with Bows 100 Points
Dropping back down to 100 Points grants the Scouts with Bows another 6" of range but they lose Piercing. The added range is nice, and at 24", the only thing you should be wary of is other ranged attacks (war machines, Lightning Bolt, other shooters). Again, the increase in range means a better chance to survive, and unlocks other options for the unit like actual harassment of the enemy.
In larger games (2k) I'll be taking all three Troops for additional testing. With focus fire, they should be able to whittle away a bit at a unit with a weak defense or a low Nerve, even with Ranged 5+ and no Piercing. With their mobility, they should be able to get into position in order to take those shots, or even flank charge as the opportunity presents. Looking forward to having these guys on the table again soon!