Bill is pretty much on in his view. There is room for a lot of experimenting and it can be much fun....and very enlightening. As long as you aren't trying to shove your philosophy down someone elses' throat, you will get along fine.
As mentioned, those diminishing returns will show up on either end; too light, and you have noise, vibration, and perhaps penetration issues.
If you have too much, you will have loss of power, excessive trajectory and diminished performance, rather than better.
There is a happy medium for each of us....you decide. My arrows have not changed in five decades, as far as fronts-of-center goes, and my arrows don't lack on the penetration side and my point-on is out about fifty-five'ish yards. That's my happy medium, and it is always supported by a bloody arrow sticking in the dirt on the far side of a mature whitetail, or a four for twenty at fifty-five yards.