Arborvitae, cedar, pine, and spruce are evergreens that are reputed to do well in heavy clay soil and all of them come in dwarf varieties. Dwarf Alberta spruce would be a nice one.
There's tons of nice flowering trees. A lovely one is our native Eastern Redbud, which gets covered in dark pink flowers in the spring. It flowers before it leafs out, which makes the display of blooms especially striking.
Other choices for smallish flowering trees would be crabapple, dogwood, cherry. Serviceberry is a large shrub/ small tree depending on how you prune it.
Find a good tree nursery in your area where they know their trees (NOT big box) and work with them re what will work best for you.