Thanks @Tim_Hobson for your helpful tips. When locking framerate with t.MaxFPS 60 there’s still an unfortunate trade-off between either super silky smooth with occasional ugly stutter (framerate locked to 60) or less smoothness with no stutter (with framerate unlocked t.MaxFPS 0 ). Based on my testing, r.VSync 1 has no effect on the probability of stutter (in fact, based on the documentation, it seems vertical sync can actually cause stutter). I’m also not sure if UE4 communicates this v-sync info to the gpu when running the game in a new window, or if vertical sync only works properly in a full-screen packaged build.
However, for my 1440p monitor which reports a TV-compatible timing of 59.94 Hz, I was able to get the most consistently smooth results (although not 100% perfect) by leaving VSync off and setting t.MaxFPS 59.94 on BeginPlay in the GameMode, and then under Project Settings > Engine > General Settings > Smoothed Frame Rate Range, I set a Max of 60.0 as “Inclusive” (selected with the down arrow beside the number), and then set the Min as “Open” which disables the lower bound. It seems to work well for the time being… 