Itunes Match ... how do I see the music that's been downlaoded to device?
You can see music thats specifically downloaded to your device, and only that music by going to:

Settings > Music

You will see an option for 'Show All Music' Turn this off. This will not delete any songs in iCloud nor change any other settings in your device or delete accounts related to iCloud or iTunes Match, this simply does what your requesting, only displaying actively downloaded music/videos. In fact, you can leave iTunes Match enabled and the results will conclude the same in your favor.

 

EDIT You can delete music thats downloaded to your phone in batches (currently by Artists only). However you can delete specific albums from that artist.

The following guide will take you to the respective settings:

Settings > General > Usage > Manage Storage (regular storage not iCloud storage) > Music 

Here you will see a list of downloaded music only. This is also where audiobooks are located! Cheers!