iPhone says no data but I have 200 Gb

That's a misconception here.

iCloud Storage no matter how large do not expand what you have on iPhone.

iPhone capacity is fixed until you buy an iPhone with a larger capacity.

To make space, you need to delete stuff you don't need on iPhone.

If your phone is low on storage, purchasing iCloud storage will not help. To create space on the phone you will need to move or delete existing content.