They will backbud on old wood if there is healthy foliage nearby...
As Wires_guy said, it is hard to control... but they respond to strategic foliage pruning/shortening quite well... once you learn how to anticipate those “rocket branches”...
I believe it could be done... it will take seasons to develop reasonable taper, seeing as thujas branch aggressively... you’d be pruning back, pretty hard whilst developing branches, the first few years....
Or leave a big sacrifice off the top.. that’s what I’ve been doing (if able) lately.