As the question is not "how low can you go", but what will make you able to ride with the smallest kite possible in given conditions - then no doubt, a huge wing, as high AR as possible, very cambered - combined with a huge floaty board, will definitelyl make you go the earliest with the smallest kite, IMO always.
A huge not high AR wing will make you start almost as early, you will hardly be able to notice any difference - and as this is what is offered (huge high AR wings dont exist, even the Alpine 952 cm2 high AR wing is not "huge", and the only one I've seen of this type).
If we are talking the really big and spikey efficient foilkites, then it is slightly different IMO, as here the most efficient wings that are faster, might be better - as these kites generate a lot more power when going fast, and you can powerspike and pump to get up foiling, thus eventually be able to ride in lower wind. For these kites when marginal, the Alpine wing t.ex would be spot on I would say.
This effect with apparent wind and speed needed does not really work the same (a bit but not nearly the same) for smaller LEI kites, so here pure size of the wing (overall lift at least) even when slow, are better.
Regarding board size, I dont see there is an actual tradeoff, as it takes a huge amount of extra power to foil, when your board is under water - not just a tad more no, but a LOT more, a couple of kitesizes more is needed.
So even if you are able to stand up on your small board, board a half meter under water or more, you will not be able to foil from there...
You will be able to get the board up to the surface for a while yes, but from there it will be an anchor so to speak.
Nor is it easier to get ashore standing this way in the surface on a small board - it will be way faster/safer/more relaxing to put your arm around your board and loop yourself into shore, 2 times one way, and then 2 times the other way on and on and on with one hand changing side on the bar
It seems some disagree about the board size effect or have otherexperiences; I am not in doubt though, the bigger the better regarding board and small kite.
In short: Wings, the bigger and more camber, the better no matter what AR for the smallest kite possible (of the offered ones), and with a spikey big foilkite, a bigger but not too big high AR faster wing is the best.
My view at least