RE: What wave board?
Most of my sailing is in the Arabian Gulf except for summers when I sail Lake Huron and Lake Michigan from Petosky to Alpena in the Lower Peninsula. I feel much the same as you do about the differences between lake and ocean water and here in the Gulf with the salt content of 5% and higher, it is even more noticable. My Arabian Gulf experiences are not likely relevant to your situation, but the boards I use in the summer when I'm home when the wind gets to 16-17 knots are an Evo 74 and a Pure Acid 80. Before I had those two boards I was on the Acid 77. I routinely start sailing either one of them with a 5.7, the PA 80 carries that size a little better than the Evo. Even though I weigh 185 I never have any problems getting the boards to plane when it starts wind hits 17 knots. By the time it is blowing a solid 20-22 knots I usually switch to my 5.3. In general prefer the Evo for working on my wave sailing and use the PA 80 more for B/J. The Evo just works better on the short period waves.
If you get a chance definitely try either the PA 80 or an E74. I think you'll be pleasantly suprised at how well they handle the Great Lakes conditions.