Gong has the best wing videos I've seen yet for pure wave riding.
Here's one but there's others too
For wingfoil, the board isn't overly technical...basically a platform. You will want to err on bigger side to start, then can get smaller as you get proficient. The pros are on tiny boards, but I don't see ever getting there personally. Especially as this is more a light wind pursuit for me. Ideal board for you may be a hypernut 5 in 1. Atomic-Chomik has a 4 in 1 for sale, but no windsurf track ... could add one though.
re: downwind wave riding...me and BradM had a mini breakthrough session on Monday, first time able to ride little windswells with the wing luffed. This was in light wind (12-15ish) and riding the waves 3/4 to fully downwind. It was doable for sure, just had to hold up the wing as you ride down the line. Then while riding you could turn the wing, ride out toeside to get a little more speed, connect to the wave behind and ride it ... all while engaging and unengaging the wing to get a little wind push if needed or luff it and just surf.
Don't get wrong, we are far from ripping, I am talking barely 1' waves and brief rides, but it was a glimpse of the possibilities. I envision CB, dropping in above the parking lot, and then zipping in and out of waves all the way down past udderland, then upwind back out and repeat, over and over. :-)