+1 for the Glide Threader Floss. I got a sample of that from my ortho, and I really liked it.

I started with the plastic floss threaders when I first got braces, but I ended up just using my regular floss without the floss threader: https://www.amazon.com/Oral-B-Complete-Satin-Dental-Floss/dp/B009H17ODE . It's really good for tight teeth, and it's actually not that difficult to use with braces even if you don't have a floss threader. Personally, I never liked floss picks even when I didn't have braces. My mouth is also small with tight teeth so I found them more awkward to use than regular floss.

Whatever floss you pick, I would choose waxed over unwaxed. Your braces will shred any unwaxed floss. There's this brand called "Sturdyfloss" which is the worst. They market it as floss for braces, but that stuff shreds like no tomorrow.