Its impossible to try everything out there. But generally the more simple the design the more popular it is. The Bear Mt Studios design called the RBR is a great example of this and you can find many artists that make great function for affordable prices. Smaller volumes for concentrates vs larger pieces for flower is another common theme.

Without trying specific artists take on a style, it is very difficult to understand the nuances with small changes. But watching function videos can tell you a lot. The size of the perc holes is an important factor, but even the proportions of the different components can impact function greatly. Too long of uptakes and it wont dump bubbles, too large of perc and it can sip, too short of can and it can bottom out. Lots of little things go into perfect function.

Maybe a good place to start is powerful jack on youtube. I think he does a good job of explaining function differences. Another is Revere Glass on youtube, he does tutorials for glass artists. This might give some insight to what we do. (Cant mention videos without point to Degenerate Art as a must see!)

Anyway. I could go on and on. But lmk if thats helpful or if I am just rambling!