1) Easy to install. I like Speedymoto's plate, springs, caps, cover. There are many others like SSR, EVR, DP, Rizoma, Shift Tech, they are endless.
2) My favorite, but again your choice.
3) Acculigns here by Nick at Motowheels. They have unlimited adjustability and look great.
Brand wise - cheap is Woodcraft, pass on the CRG and Speedys. Many swear by Sato's...
4) ASV are great, I am waiting until someone gets them in stock. Brembo top lever is the best with remote adjuster but pricey. Rizoma is pricey. CRG is the same as Pazzo in my mind.
5) Your choice.
6) Akrapovic slips, Leo Vince slips. Or just get Termi. I love my full 70mm Termi, but again pricey. Any other exhaust doesn't look right on a Duc. Comp Werkes is garbage.