On the game-map, should their fighting quality and morale be any better than normal Finnish troops?
As regards ability to shoot, I would not rate them any different from normal Finnish troops.
The same in regards to morale: operating behind the lines might require a bit of nerves, but they were prepared to scoot off to fight another day if their attack did not go the way they had expected.
That said, this sort of behind the lines action requires more initiative than just manning a trench line, so you might want to give them some bonus to represent that. Unfortunately, I am not familiar with Nuts! rules, so cannot say how to represent things in that case. Also, I would consider Finns in general as being quite capable of showing initiative, both in civilian and military life, so you might want to take that into account for Finnish forces in general (though being a Finn myself, I might be a bit impartial here). On the other hand, the Red Army forces in Winter War are not generally well reknown for individual initiative.
Also, the troops engaged in hit and run tactics might be expected to act a bit more aggressively, so you might want to give them some slight benefit in close range combat to encourage player to use them more aggressively, even though there might not be direct historical evidence for such advantage.
Operationally, they were very good at hit and run type stuff. But that strikes me as something that is more dependent on scenario design, rather than table-top quality.
Essentially yes. Being able to launch a surprise attack, at a time and place of your choosing, possibly in familiar terrain, against an unprepared opponent, should be a great advantage in a game, and this should be reflected in a scenario design.
However, getting into a position to launch such an attack is not trivial, and requires time, preparation and planning (good intelligence and familiarity with terrain helps). To make the most of the subject in gaming terms might require some sort of a game mastered campaign, where the two sides would behave rather unsymmetrically.
For example, heavy Soviet forces might be largely limited to operating along roads and open areas, while the Finnish opponent would have a number of light forces that would be much better able to travel through forested areas to strike at rear area targets. However, the Soviet side should have numerical advantage to begin with, and could receive more reinforcements as the campaign proceeds.
