SNES need dejitter mod. All models. Depending on your display, you may have better luck with a wider range of line multiplication modes, or not at all. For me, my monitors were more forgiving than my capture devices.
The N64 shouldn’t be an issue, tho. But again, it may be an incompatibility issue with your display. Try FBX’s optimzations for the N64. They are great for the SNES, and all systems he has represented, but again your SNES’ will need the dejitter mod in order to improve compatibility.