I would think that you would only want a 15-91 for FMQ because it's the only one that I know of that you can drop the feed dogs. I don't think you can drop them on a 201.
I bought the darning foot and walking foot at sew-classic.com. I haven't looked for a hopping foot but if they are out there, I bet sew-classic will have them.
I used to do all my FMQ on my fancy, newer, expensive Viking but have found that my 15-91 does a much better job. For some reason, the Viking would push the fabric and I would get tucks no matter how I changed the settings. I don't have that problem with the 15-91.... it sews perfectly every time. And, I get more even stitches, too. I'm sure others will hop on here and give their opinions, too.