The lengths can vary by about 20% depending on how tight you knot.
Luna's Fly Trap
Most knots with 4 cords become 4cm wide when using Paracord type 3. This knot will be about 3.5cm (depending on how tight you knot). Thanks to the positioning of the cords, you will get a nice pattern, which you can really vary by using different colours.
The knot itself is certainly doable, even for beginners. The difficulty with this knot lies in pulling the border evenly.