Don't do anything now, leave all foliage to hopefully drive some new root growth before it starts cooling down, and watch your watering carefully.
Good luck!
Welcome! both good choices for starter trees. Ground growing can be a good option if you want a big trunk quickly but with a few caveats, need to get the roots sorted before
placing in the ground and get some movement in the lower trunks as well. You do have to extract them every couple of years...
I struggled with fungus issues on Malus and Prunus for years, can confirm Bonide Infuse works, I apply to soil surface just before bud break and again before post hardening off pruning if applicable.
It also seems to really help prevent needle cast on Pinus if applied before the spring growth...
FWIW my only Engelmann's new growth is always blue for 1-2 years, mine can't possibly be CBS as it was collected in WA state.
Really nice job on the styling Danny