I seem to have some of the same problems. If I am feeling really bad and having trouble with tachycardia, my voice is worse. I also have asthma. So add that to the other stuff and it is not fun. When my HR increases, I have trouble breathing also. It is like a weight is on my chest. I am very exhausted when it settles down.
Yes to the breathing for me, but my autoimmune disease may be responsible for that. I feel like I have to shout to get any sound out, and my voice has really dropped in pitch. It seems to require a tremendous effort to get anything out, and is exhausting at times.
The only time my pulse is low is when I've been asleep for a while.