Love the fabrics!
It's hard for us to tell how big the design is when looking at the photos.
For sure, the size of the print helps determine how large your triangles should be. Cutting too small on a large print, could mean that fabric design which creates the kaleidos may not be seen. Similarly, cutting too large for a small print, can just give you a jumble!
What I would do, would be to cut a triangle the size you are thinking from a piece of paper. Then lay the paper with the hole, over the fabric at different points to see how much design you will see. To get an even better idea, use the OBW mirrors. Mine are just a couple of small mirrors, duct taped together.
It's a FUN process ... and you have an awesome fabric choice and colours.
Good Luck!!
If you are still unsure when you are ready to cut ... cut a strip the length of your 6 repeats and stack. Then cut and stitch. At least that way, you are only risking a small amount of fabric lost, if you are unhappy.