There's always some expensive trial and error, but one thing you can do is to sit on your bike with the shorts on (underwear underneath if you want to be able to return them). That will give you a better idea of how the chamois will fit the saddle and your body on a real ride.

My experience with the LG Neo Power shorts is that even though the chamois looks large and thick, on a ride it doesn't cause me trouble at all. I've got wide sitbones and a narrow front, so a chamois that's too bulky in front is a big problem for me. I know it's probably not the same chamois as you're asking about, though.