Kramer MPX Master Tape is a plug-in from Waves to be used inside a DAW. The software is easy to install and authorize. There are only a few controls, but they aren't immediately intuitive when you first try out the plug-in.
This plug-in can be used for a couple of different processing reasons. It can add some subtle tape compression/glue to your tracks. It can add heavy tape saturation/distortion. It can add tape delay/echo. It can even add some extra bottom end to your tracks.
Tape Hiss/Noise can be mixed in at different volumes. Wow & Flutter is also variable, which can be added in subtly or with extreme settings. I've found in practice I always turn off the noise and wow & flutter.
The main function of the plug-in to add glue/saturation to your tracks is controlled by the input level and the 'flux'. I read an interview on the Waves website that suggested using the input dial so the signal is peaking at 0 on the VU meter. This was typical of how the level was set on real tape machines back in the day. Then it was suggested to crank up the flux to achieve the desired glue/saturation.
In my opinion, turning up the input dial so that the signal is peaking well above 0 on the VU meter can achieve good tape saturation as well. Its all up to you to experiment with.
I usually use the 15'' tape speed because it doesn't color the sound to much. The 7.5'' setting adds some boost to the low-end and rolls off some of the top-end. Occasionally, this can be useful - like on a drum bus or to tame the top-end of distorted electric guitars.
Tape saturation/compression effects are useful as a cumulative effect across all your tracks - on every track, and on your mix-down bus. Kramer MPX is a good tool to take off the digital edge/sharpness of recording in the box (ITB).
I also own the Slate Digital Virtual Tape Machine plug-in. I have never used or heard the UAD tape plug-ins. Compared to VTM, I prefer Kramer MPX for heavy saturated tape effects compared to VTM. However, I use VTM more for the subtle glue of tape on more of my tracks. I also like that VTM offers a modeled 'bus' tape machine along with the single 'track' tape machine. VTM only offers a single tape model.