My generel advice is to not use ‘Fix Match’ if you can avoid it.
Put all the grunt work into getting the embedded metadata and the folder organisation and the file naming right.
Verify that the software you are working with is embedding sensible metadata into your files.
Or, even worse, that it does not blab about itself in the meta tags (‘ripped with xxx’)
If your records are kinda non-common or if you are a serious collector who has not only albums but also singles and EPs, you might want to tell Plex to give your embedded meta tags preference over what it can obtain from online databases.
One important thing is: if you have made some corrections to metadata or file names, in order for Plex to correctly sort your music, you will have to perform the Plex Dance if the files in question have been added into Plex before the corrections were made.
Look up the spelling of artist and album names before adding them into your library. This will help greatly to get proper metadata.
If you value high-quality cover art, I recommend you to obtain them as separate file in jpg or png format and add them as folder.jpg into the folder of the associated album.
It allows you to have rather large-ish cover file sizes without blowing the file size of the music files out of proportion.