I would strongly suggest cleaning up your tags before adding more via any plugins.
I also assume you have a backup handy in cases things get messy? That would be the first priority if not.
Thanks! BTW I have over 140,000 music files, so this is definitely something I want to learn more about and I want to make sure if I change anything, I'm doing it right the first time. I'm trying to understand what you are saying. So my goal should be to somehow find out the version of tags on all my files and somehow convert them all to one version?
Yup, that's correct.
These are my MP3TAG tag options.
The first one is less important to you if your tracks only consist of FLAC and MP3 files.
The second picture is important for MP3 files. By no means are my preferred options "standard," but, in my opinion, these function as very good set and forget settings.
There are no options for FLAC files, because they use VORBIS tags. However, it is possible to write ID3 tags to them, which is where the cleanup process begins.
I'm actually doing this right now. Fortunately, with MP3TAG, it's very simple.
You'll want to load the files into the window, press F3 to bring up the Filter bar, and input...
...and wait for the filtering process to finish or press Enter to start it. In a few seconds, if any of your FLAC files have ID3 tags, they will appear.
There, I confirm by clicking on a few files and pressing ALT + T to display the Extended Tabs panel, where the title bar displays the file format and type of tags present. You want to see "FLAC (FLAC)" there. To replace the ID3 tags, select all the filtered files, right-click and click "Copy tags" (or press CTRL + C), then right-click again and press "Remove tags" (or CTRL + R). Once that process is finished, right-click and click "Paste tags" (or CTRL + P) and MP3TAG will add your tags back, but without the ID3 ones present.
I haven't done this with MP3 files, but I'm assuming it works similarly, but you should test and confirm to be sure. I'm replacing any and all MP3 files I've ripped or downloaded with FLAC files anyway, so their tag status hasn't much mattered to me.
After you've cleaned up the tags, then you can determine which ones you consistently saw in Winamp that are missing from MusicBee.