Hi Goran,
Easy enough - for 10-25 knots, I'd take the 6.0 and 4.0 Echo, as you know, once you are up and flying, you really don't need much power, I was out yesterday with the 6.0 in max 10 knots of wind, day before with 7.0 in even less wind...I have the Sky 5'4" - 78kgs, I can tack, gybe and learning 360ยฐยดs...I use mainly the Aero 1750 in lighter winds, the 1500 feels good from approx 14/15 constant wind upwards. Would for sure take 2 front wings for that wind range/your weight, 1500+1750. You can shim the wings yes, with the supplied rear wing wedges, when you order the mast/fuselage set (this part has the bag+ wedges and tools).
Board wise, I would not go for 5'0" at your weight, but if you feel you will need something smaller and are often in 15-25knots, then why not...I think the 5'4" should be no problem up to 25knots, although I have to admit I have only tried a proto in the 5'0" size, since travelling got shut down this year..but have used the 5'4" in up to 25knot gusts, zero problems...let me know if more questions, otherwise get winging! :-)