"Do they grow fast?"
They grow like WEEDS, weeds on steriods
....They start growing in February, unless I leave them out unprotected all winter then they hold off until late Feb
.
I typically have to hack them back at least four times between March and June. They can push two feet of growth in betweeen hackings. They back bud all up and down the trunk--which is why they have all those warts on the trunks. Hard pruning can kill off large sections of trunks, but new buds pop in only a few weeks along the border of the deadwood and live tissue.
THey are extremely tough species and are now considered invasive in many parts of the country.
"How do Amur Maples differ from other maple species (like Acer Palmatum which I find to be too finicky)?"
See above. This species can take FAR more abuse from weather and heavy handed owners like me. I don't give them any shelter from winter cold or snow. Two winters ago, this forest and another were buried beneath five feet of snow, bent in half to the ground under the load. They were left out in temps below 10 F for weeks. I also give them full sun from March until the leaves drop in autumn. They will grow in extremely shallow containers for years. They've been in this one for over five years now and an even shallower one for a decade. They have had no health issues and simply won't die. Can't say any of that about Acer palmatum. However I like Acer P. better than this species as bonsai. Amur tends to remain very coarse in growth habits and the wood is brittle and can snap easily. Amur is also extremely stiff and upright in growth habits--and that really can't be changed all that much.