>>In the old days I used to easily be able to see if I had a printer font for each screen font, but no more.
That is true. You can no longer open a Font Suitcase. ( Me thinks Apple should change this. ) You can, however, start up from OS 9 and then you can still open your font Suitcases and make sure that you have one screen font for every printer font for your Type 1 fonts.
>>> some fonts don't show any printer fonts outside the suitcase at all
Those might be TrueType fonts. Apple also supports Open Type fonts and PC fonts. The open type fonts appeared one file at time, that is say that there is one file for bold, one file for regular, one file for italic, etc.. Fortunately, Font Book recognizes that these or all of the same type family and will organize and under one heading for you.
>>I'm trying to understand the difference between using OS9 and Suitcase and OSX and FontBook.
You know, there is an update for Suitcase which works under OS 10. I'm using Font Book though because it is free. Actually, that is not entirely true. I bought a copy of Suitcase and abandoned when Apple came out with Font Book.
>>>I get page layout files from outside my company that I work on or revise, and they come with their own fonts.
Aagh! I hate working on other people's files. BTW, if you ever change to Adobe InDesign, Adobe uses a special font folder which generally takes precedence over fonts in other locations, making your situation easier. Sorry, I got ahead of myself...let me re-read your question...
>>> Every time I opened Suitcase to work on that project, it would activate the fonts kept in the brochure folder.
Suitcase makes the System think the font is installed, or something like that, yes.
>>> they have to be installed on my computer. I can't do what I did with Suitcase, right?
Suitcase virtually installs the font. But it sort of does that remotely, without the font having to be in a specific location.
>>>But I could install the borrowed fonts on my computer, put them in a collection in Font Book
In order to keep your fonts and your "borrowed" fonts separate, you might want to place the borrowed fonts folder in one of your font folders manually, say, your home/Library/Fonts folder. That way you would know they are not yours and you can dump them later. If you double click on a font suitcase and say Install, so that Font Book installs the font, Font Book will mix the fonts up with your other fonts. That is what a Microsoft program did and I was so angry at the company.
Now, I don't know how QuarkXPress decides which font to use. I believe that Adobe does not use the same convention that Apple uses. Apple says that the fonts in your home directory are used first, then the fonts in a Library/Fonts, and the fonts in System/Library/Fonts, and finally the fonts in your old System Folder. But, Adobe chose to ignore the convention. I believe he uses fonts found in Library/Application Support/Adobe/Fonts first. Then it uses the other folders. But, still, if it finds to duplicate fonts it will compare the fonts and use the one with more characters thinking that he wanted more characters are newer fonts. That drives me crazy, sometimes. Apple has a Gil and I have a Gil and sometimes the Adobe programs will only see one so I often have to uninstall the Apple font for the Adobe program to see mine. It is slowly getting worked out, though, I think. (Anybody from Adobe reading this is sure to correct my errors.)
Assuming that core is the Apple convention of guess that you could dump a folder full of fonts in your home fonts folder. Oh! Did I say? Apple fonts folders will read fonts inside of folders. Also, if you ever switch to InDesign, the Adobe fonts folder will read aliases of fonts; so, you can stick an alias of the fonts for your job inside the Adobe fonts folder. I don't believe Apple font folders will read aliases, still.