OK, lets tackle your last question/misunderstanding. Reread the Boyer article. The physical location of image files is completely irrelevant to Aperture. You will always find and organize your images within Aperture, not using the Finder.
For optimum computer operation, you may wish to place files various places on your computer. Again, this is easily done during the Import process. There may be times when you need to relocate files after Import. Most commonly, this is done to make space on your system drive, especially if you have an SSD. This is easily done using the Relocate Masters command. Note that this makes NO difference in the logical arrangement of your images in Aperture.
4. returning the RAW files back to a folder on my regular HD
So there is no need to do any of this. Relax. I don't know if you are a pro or an amateur, but let us imagine that you are an amateur who is dumb enough to volunteer to photograph a sister's wedding.
You have your lovely iMac with a ton of RAM, your OS/APPS/Aperture Library on that big, speedy SSD, and on your HD you have a Folder named something like "My Aperture Masters."
So you shoot the wedding and now your sister, like all brides, is freaquing out. She wants the images yesterday.
At this point, the pros among us would discuss the virtues of RAW+JPEG, but we will assume that you shot all RAW or JPEG. So:
-- Import your images into Aperture. (Sierra Dragon would suggest that you first make a deep archive copy. I would tell you to never erase a card for 24 hours until your backup system has made at least two copies. Whatever, backup your trash. A bride with a 9mm or a butcher knife is not pretty.)
-- Now you have your images in Aperture, arranged in one or more Projects. To take advantage of all the speed your SSD offers, you told Aperture to store the images in the Aperture Library. (Managed Masters)
-- Go nuts. Crop, adjust exposure, convert B&W, delete, etc. Use star ratings or Albums to sort the dogs from the winners, etc.
-- Print, burn CD's, post, etc.
-- Done! Your sister still speaks to you and you have an adult beverage in hand. Life is good.
Then you look at your SSD. It is creeping up towards 50% full. As they say in West Africa, "What to do?" You remember all of Sierra Dragon's preachments about Referenced Libraries. Pick a few of your older Projects and use Relocate Masters to move them to that folder you created on your HD. While I would recommend that you exercise some good housekeeping in the way you organize that Folder, it doesn't really matter as you will only ever look for those images within Aperture, not with the Finder.
So what happened? Your logical arrangement is unchanged and your images are still safe within Aperture. All that will happen is that when you open these images for Adjustment, you may see a one or two second pause. That's it. That's all.
5. deleting the jpegs, and using much smaller Preview (stored in the Aperture library on the SSD) to look at my photos on computer (I get a bit stuck here, how can such a small Preview show a quality photo on the screen?)
Again, don't need to do any of this. Aperture generates Previews (size and quality set in Preferences) and Thumbs as needed. I set my Previews to the size of my largest monitor set the quality at 8. This produces a file of about 200-300 KB. Don't worry, when you need full quality, Aperture will read the Master.
Hope this is clear and helpful.