ITunes Match questions

Thanks for the clarification about iTunes purchases and about no longer having to sync music with my computer now that iTunes Match is enabled on both that and my iPhone. Incidentally, the music that was already on my iPhone before I subscribed to iTunes Match is still stored on the phone, I only have the Download button next to songs that I have added since I got iTunes Match, but it's great to know that I can download any of those extra songs if I expect to want to hear them somewhere where I don't have an Internet connection to stream them.

I have another question concerning what happens if I sync my iPhone with my computer now that I have iTunes Match. I haven't actually done this since I got iTunes Match working, as I had this niggling worry that all the music I've added to iTunes Match during the last week or so will download itself onto the iPhone. So can someone please clarify what happens when I sync my iPhone with the PC? Will it just back up the apps and other stuff on the phone as it used to, and leave the music alone? That's what I hope! Sorry if this question sounds a bit dumb, but I don't want to accidentally end up with a phone so full of music I can't fit anything else on it.

Hello again! I never got an answer to my syncing question in the previous post, but I know the answer after syncing my iPhone 4S with my PC lots of times in the last few months, that this sync only includes backups and app updates and that iTunes Match does the music syncing. However, this syncing through iTunes Match has led to a new issue for me, a lot of duplicate songs on my iPhone: songs that were on my iPhone before I subscribed to iTunes Match often appear twice in the list of songs in my iPhone's music app, once with the title on its own and again with a Download button next to the title, but these songs are not duplicated in iTunes on my computer. If I was to play through all the songs in my Music app, or even a small number of them, without putting them on shuffle, the duplicated songs will play twice. Admittedly I won't hear songs on the phone twice straight after each other if I put all my music on shuffle, as there is so much of it that randomising its order will separate duplicate songs most of the time, but I have a dilemma as to what to do about the duplicate songs on my iPhone. I expect someone will suggest manually deleting songs which were already on the iPhone in the past but have now reappeared a second time with a Download button due to me using iTunes Match, but, having been away somewhere without Internet recently and setting my phone to only play music downloaded to it during that absence from a place where I could use wi-fi, I know there are at least 2000 songs already downloaded to the phone, many of those transferred to it before I joined iTunes Match, and, for all I know, most of them may be duplicated in the Music app, although I haven't checked this for obvious reasons. So should I go through a long and tedious process of manually deleting one of each of the many songs which appear twice in the songs list in my iPhone's Music app, or is there a quicker way to deal with this huge number of duplicates? Thanks in advance for any answers to this latest question, assuming I get an answer this time!

Thanks very much for the answers various people have given to my duplicates issue as explained in my previous post. It's certainly strange that the duplicates happened, I don't know why, nor do I know whether a temporary malfunction of iTunes Match caused songs to be re-uploaded that were already on my iPhone, but now I'm glad to know what to do if that happens another time. I could have manually deleted the duplicated songs as one of you suggested, but turning off iTunes Match and re-enabling it was much quicker, and what's more, it looks like it's got rid of the duplicates, so thanks for reminding me of that option. I'll do the same thing again, re-enable iTunes Match on my phone I mean, if I get duplicate songs on my iPhone again in future, like I had recently.