I am not a follower of the "cut it down" to harvest method. Here in NC my hops kept producing and producing and never really stopped until we started getting frost at night. If I had cut the bine down when the first crop was ready I would have lost 1/2 my production.
I used 16ft long 6x6 pressure treated timbers for my uprights and they are burried about 3ft. deep leaving 13ft above ground and the hops quickly and easily reach this height. I have 4x4 going horizontally across the top of my vertical posts and the support ropes for the hops hang from this horizontal. At harvest I lean my ladder against the horizontal.
As for the buckets. The hops will probably outgrow the bucket in the first season. You could cut the bottom completely out of the bucket so you have your plastic ring for easy lawn care. I started a Cascade from a cutting this spring and by the end of the season I had 3/8" diameter roots growing out the bottom of the 5 gallon pot and into the ground underneath.
Plant one variety on one pole. My bines are spaced 4-5ft. apart and it is a weekly chore untangling them from each other. The arms they send out reach out 3-4ft. from the main bine so I would consider 8ft. between different varieties a minimum.