every wing is different. there's some high aspect hydrofoil wings that are worse VMG and worse upwind angles than a fatter hydrofoil but I still have fun with these thin wings because they have a high top speed. Just try a bunch of wings when you get a chance you'll understand right away.
If I am using a low aspect strutless kite and a fat surf wing, will a different wing allow better upwind angles or am I still limited by my kite?
To make things clear and all things being equal:
1) A higher aspect wing will improve your vmg but not the upwind angle.
2) Strutless (and 1 strut) kites are the worst out there for going upwind (they have other advantages) because they have a smaller window of flight.
You can't go higher upwind than what your kite will take you therefore a thinner profile/higher aspect shape which has a wider window of flight will make a difference in upwind angle and vmg.
So you are basically saying kite is limiting factor.
Yes it's a fact, just like windsurfers (RSX) and sailors trim their sails flatter for the upwind legs a kite with thinner profile will fly at a greater angle of attack. The board or hydrofoil in this case can not out point the kite as it depends on it solely for traction.
Ride bigger kites. The more overpowered you are, the more you can lean the foil way over to windward, and so the more upwind you go. The wing on the foil only lifts you straight up when it's flat. The more you lean it to windward, the more lift the wing produces in an upwind direction.
> The board or hydrofoil in this case can not out point the kite as it depends on it solely for traction.
What do you mean by this? The board absolutely outpoints the kite. That's why there's line tension. If the board points below the kite, the lines go slack and the kite stops flying.
The direction that the board travels through the water is the sum of the two vectors acting on the whole system - one is the pull from the kite that acts roughly across the wind or slightly downwind, and the other the lift from the mast/wing that points upwind. So of course, the higher you can get both of these, the better, but the absolute ideal direction for the kite to fly, relative to the rider is 90 degrees from the wind, and obviously the board can point higher than that or kiters wouldn't be able to go upwind.