this problem doesnt happen at all with the monitor on my desktop PC

I was using this monitor on a desktop PC, now using it on my work laptop and the mouse is just sluggish.  I've tried monkeying with mouse settings and its not really any help.
I thought it may be the laptops video card may just not be all that great so I changed the resolution to just 1920x1080 and its still bad.

as i said, this problem doesnt happen at all with the monitor on my desktop PC, even using the same exact mouse.

anything I can do?  is it still the video card even though Ive reduced it from 4k down to 1080p?  (even tried at 1024x768, same thing, something else has GOT to be wrong here)

Did you set the mouse DPI up higher?  It might be the monitor has enough pixels that the mouse command to move doesn't actually move much on the monitor.

Is it a TV and not a monitor? You may need to put it in "Game Mode" or let it know it's on a PC to reduce input lag.

Another common issue is laptop HDMI outputs that can only do 30 Hz at 4k, or TV inputs that only accept 30 Hz, which will cause things to feel a bit stuttery.

its always after you publicly ask for help that you find it.

its a refresh rarte problem.  my laptops hdmi can only do 30hz over the hdmi when at 4k.  I found that by reducing the resolution to 2560x1440 I was able to set 60hz and its MUCH better.

Sounds like your laptop is HDMI 1.4. If you change your chroma to 4:2:0 in the graphics driver settings it should do 4k 60hz. The downside will be text will look blurry, but it may look better overall than using an interpolated resolution like 1440p on a 4k display.

Does your laptop have displayport? You may want to use that instead. Displayport 1.2 or newer can do 4k 60hz with 4:4:4 chroma