I tried the Landr thing on a small section of a cover I just mixed last weekend. The things I noticed are that Landr plays back using the default windows audio which in my case is not the monitors.
In only tried a 30 second section of the song because my internet is so slow especially today for some reason.
I will say that it was loud. So far that only thing I hear is that the female vocal could use a bit of de-esser or some eq to reduce the sibulance. I did not notice that so much when we were mixing but that could be just because my ears got used to hearing the song. Often I notice that when I let a mix/my ears rest for a bit I hear things that I did not before.
I will need to listen again to see if it suggests any other problems with the mix.
All in all I would have preferred a separate download for the Landr but it may yet come in handy time will tell.