Hmmm... as regards the arborvitae, I think I'd choose the biggest/best trunk and remove the rest. Personally, I don't think it's a great choice for a forest style. Then, I'd just put it in the ground and fatten up the trunk for awhile!

A fukien tea at that age could probably also use some fattening up, and that's best done by putting it in the ground as mentioned above, and letting it grow for awhile with no real "styling" except for some judicious pruning.

Please remember that I haven't seen the trees in question, and besides, this is just MY humble opinion!