This is me.
I logged in with appleID and see all my music.
Im in the opposite situation though…i dont want it playing my old songs since i want the apple music version in dolby and spatial audio.
iTunes Match scans your existing library for two kinds of files. Music files it can match to what’s in Apple’s library and music files that it can’t match. For music it can’t match it will then try and upload the track so you can stream it or download it to other devices from Apple’s cloud but since that feature doesn’t support all encoded formats that you can play back you may have to convert them to get them to upload.
You can’t improve the quality of the uploaded tracks but when you stream or download the matched tracks from other device you aren’t getting the version on the device that iTunes scanned. Instead you’re getting the version Apple already has in it’s library. If you delete a matched track from you’re local system you can re-download the matched track back from Apple in the format that Apple has it on their servers.
Back when I signed up for iTunes Match when it first debuted all of my music in my library was on my PC so I did it for two reasons. First I wanted to stream my entire library from any Apple device but the second thing I wanted was to upgrade the quality of the tracks on my device that iTunes could match. Once iTunes Match scanned your music and matched your tracks with what’s available in Apple’s library then you could delete it from your local device and downloaded the track again this time from Apple using the 256 kbps AAC version of the track (with no DRM of course).
So the only tracks that can’t be matched will be uploaded and when you go to stream them or download them to other devices they’ll still be in whatever format or version of the song that you uploaded. If the track is matched then on other devices you are streaming or downloading the version of the track that Apple already has in it’s own library. All you have to do it get the same version everywhere is go back to the original device you uploaded the matched tracks from and remove the version you had on there then download the version that Apple has or you can pass on downloading it and just stream it moving forward.
I personally have a single device where I downloaded a copy of everything I own including those tracks I uploaded that can’t be matched and I make sure that computer is backed up just in case. At some point in my life, hopefully if I make it that long, I’ll be on a fixed income and when that day comes I can ditch the streaming service and go back to having digital copies of the media I love. It’s the same reason why I download every movie I’ve every purchased from Apple to the same computer. Maybe streaming will be so ubiquitous and inexpensive that I won’t have to give it the axe on a fixed income but I’m not going to chance it which is also why to this day even though I subscribe to Apple Music if I really like a song and have played it a certain number of times then I’ll still a buy it from Apple Music some other legitimate service if they have it for less (and use iTunes Match to get the version that Apple has in it’s library).