Further thoughts/brainfarts/mental doodling (I'm working, and popping in and out):
Having mentioned constancy versus intermittency (and not come to any conclusions about whether it's relevant) I could also consider intensity.
To most people (eg those who aren't for example synesthesics of some sort) the experience of shape, form, dimension and indeed colour, do not seem to be as intense, or....pronounced...... as for example, pain, fear, pleasure and so on. Is this something that may point to colour being of the former type?
A pain is, to me, definitely a feeling. Looking at the shape of an object not so much at all. Quite different in fact. The latter does not 'arouse a sensation' in me to any great extent and I say that as someone who is an artist and an architect, so I would hope my appreciation of and visual sensitivity to forms should (one would hope) be quite well developed, if only by having a lifelong personal interest and training in it. I'm also very interested indeed in film and music (as a viewer and listener) although I would not say I had a 'good ear' (or a discerning palate when it comes to eating or drinking).
But, someone may reply, that is too weak a consideration. The fact that certain experiences are generally more subtle is no indication of anything relevant to the OP one way or the other.
Furthermore, there are subtle forms of experience for things like pressure, friction and temperature, they do not necessarily have to be intense enough to cause pain. But, having said that, I have just now very lightly indeed touched my nose, and I would still say it feels like a more real and tangible, definite experience/feeling than merely looking at what is in front of me (ie this laptop) or even out the window (it's a nice day, and we have a lovely view across open countryside, but it doesn't strongly or obviously
feel a lot like anything to look at it, in the same way that touching my nose did). In short, the nature of my response seems somehow different for one sort of thing compared to the other sort of thing.
I suppose a counter-example would be a vague thought that doesn't seem to fully surface into consciousness. That's as subtle as heck, but I have no trouble believing it to be an 'in the brain only' phenomenon, even if it was so weak and subtle that it didn't surface into consciousness at all.
I'm thinking this 'out loud' this largely for myself.
And anyone philosophically interested. Would anyone disagree with the above or say that it is not the case for them?
This may be a blind alley, a dead end in the maze, obviously. In fact, I'm starting to think it is.
Provisional conclusion: neither subtlety/intensity nor constancy/intermittence are considerations that point psychological experiences one way or the other vis-a-vis the OP distinction.