Q.Crepe myrtle
I cut back my crepe myrtles in February to a 40 inch height, they now are sprouting little branches Al the way from the 40 inch top to the ground, should I remove all new growth except for the jofjest point of sprouts?

If you see side branches under three to four feet growing from the trunks of your trees, remove them to keep your Crape Myrtles from having a shrubby look.
You can actually leave the entire shrub to grow un into a natural shape, which is a tread that has started lately. Branches will bloom the entire length.
https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/pruning-crepe-myrtle-trees.htm