I’m going to try to apply this to kayak fishing. I don’t have a boat but I have a trolling motor on the back of my kayak and I can get slower trolling speeds with it (up to 4.5-5mph). I can’t cover a lake but as you said, I’ll start looking for the deepest water in my area I’m fishing in.
There are some slight differences between the species. In Buck's writings he comments that when the smallmouth become active they can move very shallow in a short matter of time.
I completely disagree with your statement that summer is a more stable period for fish than in winter. Water temps in the frozen lakes we have very between 32 to 39 degrees. There is no wind to stir things up, no electrical storms, no algae blooms and no stratification. You have less and more erratic movements during the winter because fish are cold blooded and don't need to eat as often, not because things are less stable.
I see exactly where you're coming from here, but does the specific climate dictate? I don't know if this holds true for the entire country, but winter in the SE US or in certain places in TX tends to be very consistent when compared to places like a river valley in WI or plateaued MO in the winter. At least where I live in WI it can go from rain to snow to clear to hail to sleet to blizzard to sunny to cloudy all in a matter of thirty hours. Or dealing with 40° to -40° weather with little warning of the impending coldsnap. But, maybe that's more pointing towards Midwestern weather being pretty wild for several months of the year. My local weather might be the exception to the rule instead of the standard. Up here we say, "If you don't like the weather, wait five minutes," but I don't know if that holds true for the rest of the country. Maybe I'm missing your point entirely, I'm not sure. When this guy is talking about a "stable" situation I think he means a predictable one.
