Can I save a few select text threads rather than all texts to my icloud in order to save space?

My icloud is full and I want to turn off syncing texts to the cloud. When I turn it off, how do I delete all the texts on there in one fair swoop rather than one at a time?

Also, once all are deleted and I free up 100 GB of data...yep...100GB you heard me...its awful then can I choose to download only a few select text threads rather than all?