The question is, is the engine idling rough or is there a vibration being transferred to the chassis and nothing wrong with the engine.
A bad motor mount will not "affect" how the engine runs (unless 30+ years of being a gearhead are all for naught...in which case I'm very interested in this phenomenon).
Again, if you saw the engine "jump" as in seemingly unrestrained movement, not just "twist or flex" a bit, the motor mount is shot.
Keep meaning to look at the mounts in my 2016 Silverado as I'm sure they're the same or similar, but generally a front engine, north south transmission vehicle is a fairly straight forward replacement.
Motor mounts are generally bolted hard to the frame and engine with a "bonded" rubber isolation structure between the 2 sides of the mount. Additionally, there is generally a metal "stop" built in, that if the isolation structure breaks or comes loose form either side, the engine will move, but not alot before the stop or catch keeps it from twisting excessively.
If that isolation part is broke/gone/degraded, I could see engine vibration transferring to the chassis being a perceptible condition.
On the same note, I've driven vehicles in the past with broken motor mounts fir a while without issue, as long as I accelerated slow and didnt try to twist the engine out of the car.
