I started out with the Luna Display, only to discover that it would not work the way I needed it to. I have an old 17" iMac (2012: OS Mojave 10.14.6). There is nothing wrong with the computer, I just don't have room to have two 17" iMacs on my desk. Anyway, on that computer is old software that I can no longer access on my newer 17" iMac (2017: OS Ventura 13.3.1). I use that newer iMac on a daily basis for work that requires the latest OS, so it needs to have primary placement on my desk. I needed to be able to access the 2012 iMac on my 2017 iMac.
I was greatly disappointed when I found that the Luna Display device I originally purchased would not work. Luckily, I contacted Astropad for help! Their representative told me of another Luna device, the Luna Mini DisplayPort.
It works great! Sometimes it takes a little while for some things to work (like when I first start it, I cannot drag and drop), but after an undetermined length of time (I have not timed it), everything I have tried so far works. It is not as smooth as working directly on the 2012 iMac, but it is not so "unsmooth" as to be problematic, even in the graphic design software that I mainly use.
I have only had the Luna Mini DisplayPort for a short while, and it has already saved me time because of that easy access to my 2012 iMac!