I've been doing a test piece and I was wrong - you can (and maybe even should) quilt right up to the seam line. Then wadding and backing are trimmed to match the top, which should be a straight line. Then the next top strip is placed RS to RS and the next backing strip is placed RS to RS, so 5 layers, and stitch the seam with the usual 1/4 inch seam allowance.
The next bit is a bit fiddly as it has to be right.
Flip the backing open, place the second strip of wadding (which must have a straight edge!) over it and but up to the first strip of wadding and flip the second top strip over and pin the next bit of the sandwich. Use plenty of safety pins near the join. Quilt second strip.
It is good to have quilting going right up to the seam as it holds the wadding securely in place, and taking FMQ over the seam helps blend it all in, but it doesn't have to go over.
So, maybe it's back to the previous plan of FMQ over the lights and parallel lines over the darks, but some thought is needed about the direction those lines will take.
It's the first time I've used the 201
for quilting so there's been a bit of experimenting. She was happier with the feed dogs up and stitch length set to 0 than with the dogs down. The tension on the presser foot needs to be very low.
I tried with the old Singer hopping foot but didn't get on with it.
But, the modern Husqvarna open toe (low shank) foot I've used before fits and works well. Best thing is that the stitch quality is so much better than I was getting with FMQ using the Husqvarna.
I've also had the Husqvarna walking foot on the 201 and it's OK.