For most applications, there is no clear tape choice worth considering. Use Oracal's own high tack paper, or R-Tape or Transfer-Rite.
Some beginners like clear because it gives them more confidence lining up graphics. Experienced techs prefer paper for its easier handling.
651 is my favorite short-term calendered vinyl. I use it for promo and real estate signs. It is slightly thicker and more rigid than cast vinyl, making it a breeze to weed. The adhesive is aggressive. I use it on flat surfaces only.