In Joensuu,Finland was 4 days 3-10 m/s winds and surface was 0-10cm wet snow.
in 3-5 m/s I used 18m2 Guerilla, 4-8 m/s 13m2 guerilla and 6-10 m/s 10m2 guerilla, I weight 85kg and use snowboard.
if there is less than 3m/s guerillas sucks, I believe that G's profiles are so "bad" that they just don't fly good enough.
Surface was not good and because I have only helmet, I used small kite. If you have good protection or (better if) there is more snow I woud say that 18m2 is good for 3-6m/s, 13m2 5-10m/s, 10m2 8-??m/s
Of course you can use 10m2 already in 3m/s, but you can't jump properly before there is that 8m/s :-)
G's are very easy to launch if there is less than 10m/s wind and if there is snow (I have no experience in stronger winds in winter), If you are on ice with no snow, I don't know how launching would work whitout any assistance.
Taking kite down is possible just pulling QR, or having someone to catch kite.