Hi there, glad you like the forum, it helps us too, to understand our customers needs better!
what is your skill level/your focus on, i.e. early planing, manoeuvres, or more top speed?
Here is a good comparison between Blast and Jag, scroll all the way down:
https://www.fanatic.com/windsurf/boards/freerace/jag-ltd
So I would say for 10 to 18 knots you need a bit bigger board to get planing, even if you are fairly light. But then you also mention smaller sails up to 22knots. The Jag is a Freerace board, so it´s all about top speed, fast gybes. 5.0 is a fairly smaller sail for the 68cm width and style of the board. The Blast on the other hand is narrower at 66cm, definitely better in stronger winds for your weight/smaller sails, has a foilbox too, is more oriented towards manoeuvres, quick accelerations and excellent control in chop.
Foiling is similar to normal windsurfing or SUP, in that as soon as you have mastered the basics, you can go down quite quickly on board size, once you have learnt how to pump the board and foil onto the plane. So I think with the Blast, that even though it´s a relatively small board for 10knots, that as soon as you have the very basic foiling skills down, it will be big enough for you.
On the other hand, if you are used to riding faster boards like the Jag, then it is also an option and 22knots is not that much wind - but the 5.0 is a bit small for that board, to be quite honest - ideal sizes are approx 5.7-7.7. Whereas the Blast can handle a huge range of sails, 4.7-8.4 is alll possible on it.
I would lean towards the Blast!