
No 3 "A bit of elegance" has a nice sheen to emphasise the sheen in the plum bark and I think that the pot colour would enhanse the plum blossom. (possibly with the addition of a rock if the roots lend themselves to "Root-over-rock", to give the composition a bit more elevation, speaking as a rock-a-holic).
No 4 "More elegance" doesn't work for me because of the pot colour and matt finish.
No 5 "Old Japanese pot" has the elegance to work with the tree's style, the depth would add elevation to the planting lifting the lower branch and giving good seperation from the viewing platform and the low sheen finish and colour would work well with the plum blossom and when in leaf.
So for me the choice is between No 3 & No 5.

I look forward to seeing it potted whichever way you chose to go.