The thickness is taken from the spine so it is no mark for the edge angle.
Every angle you have mentioned is right for any steel you find on market unless you want a thinner edge and angle. Than you should look around carbon steels.
Butt in between 30 or 40°, don´t worry, go for what is more important for you. If you need a stronger but little less cutting edge because you cut tin cans any third day or you just want to feel you could do this, take 40. If you want a very sharp edge take 30.
O do a compromise and put it together. A main edge bevel of 30° and the very very edge finished on 40°. That´s what the Sharpmaker does.
Considering the blade geometry you find in general that a blade, thick over the edge needs to have a small edge angle like 30° or little less. If it runs out thinner, you can use a greater angle for durability.
For example the BM 806 D2 is a little thick over the edge (around .8mm). The 550 is thinner. You can add a large angle on the 550 for a durable edge and still have a knife that will cut great. The 806 works better with 30° but this angle is somehow weaker.
Hope this helps.
I found, that edge chipping is more detemined by the steel. I tried it on a d2 blade. Every angle between 30 and 50° i have taken showed me the typical micro chips. So i ended up with something around 35° and with it i am satisfied.
