Here are relevant sections of chat with Apple Support person "Randy." (I'm Mark)
Randy: iTunes Match is designed, when you enable it, to disable the local content in lieu of accessing it via iTunes in the cloud.
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Randy:
 You can have songs available for off-line play.
Mark: 
How?
Mark:
 And is there any way to get commercial free iTunes radio without enabling the other Match features (that I don't need) on the iPhone?
Randy:
 On your phone create a playlist and at the bottom there is a button or selection to download all.
Mark:
 So I download from the Cloud instead of my Mini for off-line play?
Randy:
At this time there is not a way to enable pieces of iTunes Match selectively.
Randy:
 Yes. Download from the cloud. Also, when you play songs in iTunes Match on your phone it stores them in the cache for off-line access.
Mark:
 I think what I need would be a good option. It seems a little crazy with Match to have to download from the Cloud for offline play when I can do it so much more efficiently from my Mini without using bandwith.
Mark:
 Just so I'm clear, can you tell me how to download my ENTIRE libary to my iPhone for off-line play?
Randy: 
That would easiest by creating the playlist on your computer, then drag all the songs or albums to the playlist.
Randy:
 Next, give it a few to update on your device, the download all for that playlist on your phone.
Mark:
 OK, I'll try that. And when I add new CDs to iTunes my Mini, do I have to do the same thing? In other words, synching locally iPhone/Mini no longer is of any use?
Randy: 
Newly added content should upload to iTunes in the cloud and you can access it from your phone. You may even want to make a play list and when you phone refreshes iTunes Match, you will see it on your phone also.
Mark:
 OK, thanks for your help. Oddly for Apple, this is complicating my life rather than simplfying. I'll have to see if commercial free Radio is worth all this hassle.
Randy:
 I understand.
Mark:
 With all due respect, this seems like something a Microsoft engineer would have cooked up!
Randy:
Thank you, Mark, for contacting iOS chat support. I hope you have a wonderful day! If there is nothing further I can help you with, please click the "End Chat" button on the upper left corner of the chat window. There will also be an option for email if you would like a record of our conversation as well. We are here 24/7 if you need to contact us again for anything.