As part of your biological exploration, look up the term SAPROPHYTE.
You have a superb example.
The oak here is just coming into leaf. There are huge cracks in the clay under it. We need some rain soon.
If you've only just planted it, it should be fine to move it.
They look ready chitted. Bury them 18 inches apart and 30 inch between rows. Try not to knock the shoots off. If you have any compost use that to mound on top as they grow.
Thalictrum prefer some shade. It may improve once the roots move out from the pot shaped ball. Keep watering. The best time to move it would bein early spring just as it starts growing again. If you chop it, you will lose this years flowers.
Take them both back. Not fit for purpose.
Weeping willow will suck it up. Only for big gardens well away from the house.
They look pretty poor specimens to me. How much did you pay for them?