The 1500 is a bit small for light winds, t, I'd get that one later for the stronger winds/any wave use. Wingfoiling in fact is more like kiteboarding when it comes to going faster/high performance - you want the smallest board possible, I guess you have seen the size of your average race kiteboard, which they use in as low as 4knots - tiny.
Windsurfing is quite different - the top racers are using huge boards, 10sqm sails and then tiny front wings, to get the most speed - so you compensate for the small wing with the bigger board/sail. This does not really work in Wingfoiling at all, as the bigger the board/the slower less performance you have. If you want to go in lighter winds then the best way to do it is having a board which is a 10-15L over your weight (5'4" x 95L) and a big front wing - 2000/2500? if it's super light, then the 5'8" as mentioned will be a good learning/advanced riding compromise!