MTS

OK, full disclosure - I send most of my quilts out to be quilted on a longarm, however, I absolutely never ever say "do whatever you want." I go in with drawings of squiggles,swirls, motifs (I hate feathers), thread colors, border treatments, etc and the conversation begins.

I have no idea what your skill level it, and how comfortable you are FMQ-ing, so let's just assume we're working with straight lines.

I'm just jabbering here....

On the rare occasion I do do the quilting, my actual skill level consists of the Bernina #4 stitch - see picture below.
So if I'm ever quilting in a straight line, this stitch is very, very forgiving, especially if you're doing it in the ditch.
It also adds a bit of interest, and movement - there are enough straight lines on the quilt from the piecing. Do you have a stitch like this on your machine?

I definitely like the double lines better, and I like how the lines make a grid that's different from the actual piecing grid. I like that a lot.

I'd go around the red square as well. And put a path through the white squares and black squares. I like a LOT of quilting.

You can switch up the thread - use white on white, red on red, or black on black - same for the borders, if that's what you're comfortable with.

Maybe in the border on the black you can just go around a few times (see my picture). It goes very quickly. ;-) Use the walking foot to guesstimate the distance between the rounds.

Or you could just continue the grid pattern from the blocks into the borders.

I'm not crazy about doing all straight stitching in the middle and then some feathers or something in the border. But that's my aversion to all things feathery. You know, like some folks are with clowns. I've just never been of fan of them

Like I said, just me jabbering. ;) ;)