ah, yes sorry forgot to comment on the Jag! :-) if you look on a scale according to rider level (as shown in our board overview -
https://www.fanatic.com/windsurf
with Advanced on the right (Blast/Ja) and intermediate on the left(Gecko), then you'll see the Gecko is for intermediates/light wind/planing/learning footstraps. The Blast is for the more advanced free rider, hence narrower and better for tight manoeuvres/less about maximum planing, more about performance. Finally the Jag is all the way on the right, closest to the pure Slalomboards the Falcon - the Jag is positioned as a "Freerace" board, so you can partner it with your S-type SL sails - but it's for sure a more difficult board to master than the Gecko, as it has more outboard footstrap setup and is made for someone who has relatively good skills in slalom, who just wants an easier board to blast around on than a pure slalom board.
Planing wise, the Gecko 122 @77cm will probably still plane earlier, even if the tail is narrower than the Jag @75cm, as the Jag has a narrower centre, cutouts and a slightly higher overall rocker. So I think with either of the 2 Gecko´s should be fine and you should choose the size according to the main wind range - certainly 122 will be better in 10knots, but as you are quite light you could also get away with the 110 too..I would favour the 110 for your weight. If planing/sailing often in 10-20knots, take the 122, as this will help advance your gybing skills a lot!