Nice,
The pot is a "Cascade Pot" a style that was really popular in the 1960's and 1970's for bonsai in USA. It is used for full cascades, where the descending trunk or branch is longer, or descends deeper than the height of the pot. I happen to really appreciate this style, so I would not shorten your descending trunk at all. Just visually estimating the size of the pot and the tree, that pot is sufficiently large enough to allow the juniper to double or triple it's volume of foliage.
Junipers do not like to be repotted every year. Trees are not like orchids and other houseplants that like annual repotting. The most frequent I would repot a young juniper is once every other year, and my more mature junipers I will allow to go 10 years without repotting. Your tree will grow better if you allow it to go 2 to 4 years without repotting.
for pruning or wiring, I would remove some of those little branches that are growing perfectly vertical, especially in the upper third of the tree. I would not wire in spring. I would wait until middle or late summer to begin wiring out this juniper. So you have plenty of time to contemplate how you would do this. So for the next couple months, just let this continue to grow, pruning only a few of those perfectly vertical little shoots, and that is about it.
Eventually, when you wire in late summer, you want no section of trunk to be perfectly straight. The length of the trunk should curve back and forth, with no straight runs. The branches should move to the sides and front, not curve upwards. Watch videos, and visit or join a local bonsai club if you can.
Nice little tree.