I have two Chinese Elms that escaped their pots a few years ago..
Should I just chop them down a bit from top? Was thinking of digging them up next winter..
These look good for broom style starters. Elms throw lots of buds around the exposed cambium when chopped. Chop the trunk horizontally right where you want the branches to start. When hundreds of new shoots sprout you can thin then to 3 - 5 well placed strong shoots and let those grow for a year or so then chop them a bit higher to force ramification.
Definitely dig them next spring or whenever appropriate. I suspect there will be some thick roots so a sawzall or axe will be helpful here. Chop roots quite short - back to a few horizontal lateral roots. Chinese elm can cope with massive root reduction.
Layer this summer if you like and think you really need more but how many Chinese elms can you use? And is there any branches that might yield good trunks? I can't see any with taper or good bends. Personally I'd just get on with developing the lower trunks. The sooner you start that the sooner it will be ready to go in a pot. Layering will just push the timeline out by another year.