Normally, people just work with the parts they want or can afford and put them together as best they can to get the look they want...
Every part, even parts of the same company / brand, have variance, so you'll never be able to say "if i put 50 mm origin fenders with xx brand wheels of this size" it'll always look the same, it won't. It depends on how you install the fenders, on what brakes you have, on so many other factors that you just have to put it together and make adjustments as needed.
Also, i disagree with you saying "start with fenders and then get wheels", i think you should start with the wheels you want and make the car fit them. That is if you want good fitment.
If it helps, i run the following specs (not saying i have great fitment, just an example):
front
18x9.5 5zigen fn01r-c hot version ET 12
235/40/18 tires (don't remember the exact brand, which also affects fitment)
stock fenders with roll / small pull
rear
18x10.5 Varstoen 2.2.1 ET 0
245/40/18 tires (again, don't remember what brand or model)
30mm Bings overs
