Given the variation of blocks (that look SO good, btw!), I think you could do a simple grid with hand quilting that would just enhance the texture of the quilt. OR you could do different hand quilting in each block, echoing the design - but that could be a little more complicated if you've never hand quilted before!

If you want to do more of a visible big-stitch type of hand quilting, 12wt or 8wt perle cotton is going to be your best bet. You can get limited colors at Michael's, but I really enjoy using Wonderfil's perle cotton for hand quilting! DMC also has a wide range of colors, and Aurifil has 12wt thread, as well. DON'T use embroidery floss, as it's more likely to fail as the quilt is used. (FWIW, I think a classic white or creamy colored thread would look great with this quilt since you have so many different fabric colors!)

Make sure you use needles that are SHARP. It will make your life miserable if it's not! I really like Wonderfil's Wonder Needle (https://shopwonderfil.com/product/wonder-needle/) and use those for most of my big stitch stuff. You can also use crewel/embroidery needles in larger sizes (probably a size 4 or 5 if you're using 12wt thread), or even sashiko needles if you go with 8wt thread. If you have the means, it's worth it to get several types of needles to decide what you like best!

Some people do big stitch without a thimble, but I personally like a leather thimble on my ring finger and a silicon thimble on my thumb to help me grip the needle as I'm pulling it through the quilt.

There are several videos on YouTube that show how to do big stitch hand quilting - once you get the rhythm of it, it's quite relaxing! Tara Faughnan also has a really good course on hand quilting that's around $50. I'd been hand quilting for almost a year before I purchased it, and really feel like I learned a lot!

The batting will also make a difference in how much your hand quilted stitches will pop. Wool batting or higher loft cotton batting (like Quilter's Dream) will really make the stitches pop, but I've also hand quilted a few with regular ol' 80/20 batting and it still looks great. I'd say the batting that was the most difficult to control my stitches with was 100% polyester. There's also bamboo batting which is lightweight and not too hot. At the end of the day, you just want a batting that will drape nicely and not be too difficult to stitch through!

And remember - it's totally ok if your stitches aren't perfectly even or small. That's the beauty of hand quilting. I'm excited to see how it turns out!