1) Pump vs. Semiauto? - I prefer Semiauto, because I LOVE the M4, but either one is fine.
2) Barrel Length? I prefer 18-22" tubes, shorter, easier carrying, little easier to swing in tall grass without drawing attention.
3) Most accurate load? Benelli Super Nova and M4 - with either Patternmaster wad-strippers or 0.680" chokes (almost regardless of choke brand), Federal #4 buck tends to give me the tightest pattern and best balance of KO power vs. shot count. Nod of respect to Improved choke with Winchester Super-X 00Buck, which I started out using as a kid, and have taken many, many coyotes with over the last ~25yrs. Never my first recommendation, but it's the first thing I reach for if I run out of #4 Buck.