All species will fuse if held together long enough.
Junipers will fuse without cutting the bark but it will take much longer and can be hit and miss. The trunks need to be tied tight for a year or more and the ties begin to cut in and mark the trunk. Removing some bark at the contact point makes it more certain and speeds up the process to just a few months.
Ties right around the trunk like shown will cut off circulation and can kill part or all of the trunk if left too long so please check regularly if you choose to follow this tie method.
It will work with any sized trunks but thicker trunks are much harder to bend if you want some shape in the trunk.