Sorry for the blue ink inserted into your words but it seemed to be the most simple method of communication without getting too wordy.
If you've misspoken or if I have misunderstood, I would appreciate a clarification.
Thanks.
I'd prefer to not call upon information that I heard second handedly but I may have to in this case. I apologize if any of the names are wrong below.
I wrote up a reply and realized that I did miscommunicate my thoughts.
What I was going to mention was something Tom Simpson calls the Happy Shot (or something similar) and it's designed to get you to understand your base speed. You take the CB and spot it, then stroke the CB letting the weight of the cue determine the speed of the stroke so the CB should end up within a diamonds distance on the table every time you stroke. That becomes your base speed, and reference speed on future shots.
Let's say that a players base speed is 2 and a half table lengths, if they're cutting a ball thin they can expect to go that distance. If they need to only bounce 1 table length then they know to lessen their speed. If they need to go longer then they know to increase their speed past letting the cue weight do all the work.
That was my point. I hope I wasn't insinuating that cue weight does all the work, just that knowing how far the CB does when you do let the cue weight determine the speed is important and serves as a reference. I don't think anyway disagrees that arm speed changes from shot to shot, or that arm speed is negligible. But you need to gauge your arm speed vs. a consistent speed (the cue weight).
As for why my stroke changed when I gripped more firmly, I don't know why this was the case but it was fairly easy to see and notice it. I remember John Schmidt talking about loose grip vs. firm grip on the Tar Podcast with Corey and his reason for doing so is my reason for doing so. A firm grip does not work for me and it takes away my feel and touch on shots.
Again, I wasn't saying arm speed is unimportant or negligible; it's very important and it changes shot by shot. But, you have no base/natural/reference speed if you haven't ever let the weight of the cue determine one for you is all. I struggled with this concept for a while, and I struggled to actually find my base speed because I was incapable of completely letting the cue do the work.
Then, from my martial arts background. It's easier to throw a straight punch when your hand is relaxed, and much more difficult to do when your hand is tense. I think the same applies in pool. With a firm grip it feels like I'm trying to direct the cue, with a loose grip it feels like I'm letting the cue fly straight. This is just my experience with experimenting with how different grips feel for me.