compatibily with ubuntu and wd red pro

What do you mean with 'compatible with Ubuntu'? You can't install Ubuntu on the NAS, but you can access the shares from a Ubuntu system. (Make sure samba client is installed on Ubuntu).

And yes, that disk will work on a '542, yet there is a problem. The NAS supports a maximum volume size of 16TiB, so if you intent to create a raid0 or raid5 array of several 16TB disks, you'll have to create several volumes to utilize all that space.