Much of the tilled in turf grass is going to keep growing, it would have been better to scrape it off. Before you plant you should try to comb or sift through and remove as many pieces of any size as you can.

A good general distribution of the plant types would be evergreen shrubs on the ends, deciduous shrubs between those and the center, climbing plants* at the back (if you are willing and able to use those) with the non woody plants occupying most of the center.

Even if it is decided the position is too hot for hydrangeas in your climate you could probably still use abelias for summer bloom. These are another frequently sold shrub that has a variety of selections on the market. Not the same large flowered appearance but still profuse and long flowering.

*Clematis, honeysuckle and climbing roses would be typical examples - especially for a summer flowering scheme

Yes, we still have a lot of work to do to the bed before anything gets planted. My husband just wanted to play with his new tractor - ha!

A Tennessee Landscape Contractor's Guide to Hydrangeas

https://extension.tennessee.edu/publications/Documents/W304.pdf