You mentioned the variable ghosting, which absolutely is a monitor problem. Either the algorithm determining how much to overdrive the pixels from frame to frame is bad, or the panel itself is too slow for overdrive to work effectively without being noticeable. There may be a setting you can turn down in the OSD to improve performance, as many gaming monitors come with this set too high out of the box.
My suggested fix should still solve your other problem, which is the wild swings in framerate. Bouncing between 200 is 100 certainly is jarring, and capping your game's framerate to make those swings smaller or nonexistent will fix it.
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You mentioned the variable ghosting, which absolutely is a monitor problem. Either the algorithm determining how much to overdrive the pixels from frame to frame is bad, or the panel itself is too slow for overdrive to work effectively without being noticeable. There may be a setting you can turn down in the OSD to improve performance, as many gaming monitors come with this set too high out of the box.
My suggested fix should still solve your other problem, which is the wild swings in framerate. Bouncing between 200 is 100 certainly is jarring, and capping your game's framerate to make those swings smaller or nonexistent will fix it.