Hi Giles, mainly for waves then the Allwave could be a good option - the 9'3" is a pretty big board, I use the 8'8" or 8'11", 135/145L, plenty big enough for 78kg, 183cm myself. Maybe get the slightly longer 8'11" then for combining with Flat water, otherwise if you are doing a good combination of both, then the Fly 9'6" is a great board for paddling on both flat water and in the waves too. 151L stable, narrower tail and turns great, easy to catch waves, paddles better in a straight line.
Re the sails, feel free to go to DTW Social media channels. When we tested the Grips and FreeWaves, we found the sweet spot on the Grip 86 is approx 5.0-5.3, down to about 4.0, all in Super Hero. And then for the FreeWave, go for a Super Star in 5.7 or 6.2, for more power/lift, my wife/daughter ride the 5.7 on a Freewave 95 and a Blast 115, works great.