Fig tree starter root-balls can be planted at any angle.
Yes, I did that before, so that the main lateral shoot was vertical
(you can also easily straighten them up using a garden stake).
As for depth; planting at same exact depth is very common.
I have planted "deeper" before, and mostly I do it, if the
"new" growth lateral shoot is close to the surface; my
thinking being that new roots will eventually develop
from that node ( a plus).
When planting/potting-up a young fig root-ball; do, do score-it
top-to-bottom (choose the less rooted side) to cut any
circling roots - the tree will be very thankful when mature
(no self-strangling).