Thanks for everyone’s input, a common thread here but hard to tell if they are all the actual same.
I don’t have temperature specs, but as I mentioned I am running at 29% and lower CPU with lots of RAM overhead, no unusual and extremely low Disk activity. When Building lights the CPU pegs 100% and my fans kick into high gear noisily, so I no there is no thermal. My specific 980GTX video card and all current drivers the culprit? Who knows.
So to be a broken record, no unusual hardware activity, it just putts along normally. Hiding and showing the viewport turns off/on the stutter in the rest of the editor like a switch (like a video/graphics/driver problem). Unchecking “Realtime” turns off/on the stutter in the editor like a switch. I have never un-checked the “Realtime” in any version of UE4 for years - except in 4.19 as a last resort, and of course simulating it returns as Realtime is back on. And a Packaged exe runs perfectly, no problems, only the editor hangs.
I appreciate everyone’s eyes on this so far.
So what is the viewport in 4.19 reacting to that hasn’t been an since 4.16? Once again I implore Epic to suggest a rendering/viewport setting(or?) to hopefully negate this new incurred behavior in 4.19, hence the reason I am posting in this “Epic Feedback” forum.