You'll have to make allowances for me here, it's been 6 or 7 years since I converted everything to LED's and the '15 came with them, so my information may be dated.
As I remember, my '09 ultra came with an H4 bulb in the headlight and H3s in the spots. The Kuryakyn headlights (at least the ones I installed when I got the bike home) required nothing extra. They were a direct replacement for the 7" QI units. I imagine the new ones are as well.
None of my conversions required wiring upgrades. I did have to play with the plug connection when I replaced the spots on my '03, but that changed with the Kuryakyns I put on the '09. They were a direct replacement.
Finally, if I remember correctly, (Here comes the disclaimer. I haven't checked in the last few years.) JW Speaker makes H-D's lights and Truck-Lite manufactures for Kuryakyn, so go where you get the best deal on the one you like most.