I'm not a hand tool guru, but here is my understanding...

A standard block plane has a 20 degree bed, and the standard bevel is 25 degrees for a total bevel angle of 45 degrees (a low angle is 12 and 25 for 37).

The advantage of using a 'microbevel' of 1 to 5 degrees is that there is less material to remove when you need to resharpen the blade. 5 degrees of microbevel seems excessive to me.

Increased blade angle tends to add a scraping vs. cutting component to the 'mix', it increases the amount of labor necessary to do the work, but reduces the likelyhood of tearout (in wood other than end grain). In end grain, a low angle is 'better'.

Reducing chatter is a function of blade thickness (thicker is better), sharpness of the blade (sharper is better), wood being planed, depth of cut, and throat opening. I'd start with making sure your blade is sharp, then reducing the depth of your cut.

I would leave your smooth plane alone (can't say anything about the spokeshaves, but I'd probably leave them as well). Changing the bevel angle on a bench plane (like a smooth) has no effect on the cutting angle, as the bevel is face down. The cutting angle is determined by the angle built into the frog.
the bevel just keeps the back edge of the blade out of the way.

Hope this helps.

Aaron