If you want the custom Flash on Clash you can email the customs shop asking for the custom LED, though it may cost a little extra, otherwise you cannot change the flash color.
The wrench should be included if you purchase the entire saber together. If they do not send you a wrench, it is a size 5/64" Allen Key.
The most realistic is probably the Standard. If you want it a bit more shiny, then the Polish+Clear coat is the way to go.
As for the covertec, if you plan on using the D-Ring to attach the saber to your belt rather than the covertec know and belt system that saber forge offers, you can purchase a D-Ring clip from The Custom Saber Shop
Here