Headweight feel is both related to and independent of, the swingweight and the MOI of a golf club. Let me explain.
No question if you take any assembled club and add weight to the head, you do increase its MOI and you also increase its swingweight. But if you were to lengthen the club without adding any weight to the head, you would also increase its MOI and increase its swingweight, and you would also end up with a little different headweight feel than if you just kept the length the same and added weight to the head.
In other words, it is very possible to have two clubs with identical MOI but they display a difference in headweight feel - just as it is very possible to have two clubs with identical swingweight that both display a difference in headweight feel.
Not to overcomplicate this, this is why in any fitting for any golfer, it is important to first find the best length for the golfer, and then to find the best shaft weight for the golfer based on your evaluation of their total weight needs for their strength + transition, tempo and release considerations. Finding the right length is much easier than finding the right shaft weight/total weight for a golfer.
At any rate, once the right length and best judgment for shaftweight/total weight is decided upon, then comes the search for the best headweight feel to go along with these first two.
This is why at present, I like the procedure of using a test club built with the right length and best judgment shaft weight, and then using gradual increases in headweight to try to find where the golfer both achieves a higher percentage of on center hits AND where the golfer also tells you they are liking the feel of the headweight versus their tempo and strength characteristics.
No question that much of the fitting of total weight + headweight feel is judgment and trial and error. I wish it were different, but at present there isn't any tried and true measurement that can tell us without a doubt what shaft weight and what headweight with it is going to end up allowing the golfer to achieve their best swing tempo and best on center hit performance.
I can use good educated guesses from my evaluation of their strength + transition + tempo + release, but we still have to experiment and observe the results as well as listen to what the golfer tells me.
While I am a decent ball striker at times, I personally cannot feel a big difference between a one flex difference (10 cpm's butt frequency) between two identical shafts or a 3 or 4 gram difference in headweight...but I know there are golfers who can.
The main thing I try to get across to a golfer when doing the fitting for total weight and headweight feel is to first explain that too light means you have more of a tendency to have your tempo get too quick or you have more of a tendency to think that you need to slow down. And Too heavy means you sense that it really takes more effort to swing the club or that after a few hits, you start to feel like it is too heavy or that you do have to make more effort to swing the club within your desired tempo/rhythm feel.
Putting those concepts into the golfer's mind as they go through the fitting then helps them to give me at least some feedback regarding what I need to know when it comes to increasing or decreasing weight.
Also with some golfers, usually the less experienced or the lesser skilled players, when I talk about these aspects of FEEL, many times they are not going to know what I'm talking about because they cannot themselves relate to these differences yet in their clubs. This is why when I talk to a golfer about the various aspects of feel, if they look at me like they have no idea what I'm talking about, or if they specifically tell me they don't notice such things, then I say "fine, that's OK" and use my judgment based on evaluating their strength + transition force + tempo to make these decisions for them. I then watch for improvement in on-center hits with an impact label while doing the test club thing.