Welcome from Oregon! Congratulation on the upcoming birth of your new GD! I read that you are new to sewing and have a new Brother XR-7700. I also read that you are familiar with rag quilts but you have only made one, as you stated. You are undertaking a huge challenge using the Minky fabric for a rag quilt. 1). You are new to sewing. 2). You have a new machine.
(Excuse me when I had to walk away; I was afraid the lightening bolts from the sky would strike.) Believe me, I have to keep my wording as to not offend anyone. (For anyone concerned about my content, I am copy/pasting this post into emails just in case I need it for my defense)
Unless you are severely underestimating your abilities or your confidence level, I believe that your choice of Minky will not bode you well. Many people do NOT have a walking foot. A rag quilt does not require a walking foot.
I realize this perhaps could be my last post, but I have spoken. I hate to see people wasting money on a fabric or an special foot that is just not right for their skill level. *Please see the above paragraph before you pass judgement on my opinion.