rainbowcat, I think, like many people, you are still confused between iCloud and iCloud Drive. Have a look at the Screen Shot below of my iCloud Settings:
View attachment 37736
Note; Optimise Mac Storage is off.
iCloud Drive is turned on. iCloud
Drive is an option in iCloud as are all the other items in the list.
Note; My Photos is turned off. I think yours is turned on. Please check this.
Note; This is not the same as iCloud Photo Library which is a complete backup of all your photos accessible on all devices and stored in iCloud.
By having mine turned off I must manually select what photos I have on each device.
Turning it off (if it's on) will not delete photos, just prevent them from syncing.
All the other items that are turned on like, Contacts, Calendars, Reminders, Notes etc, etc (pretty much all of them) are just
synced between devices, not
stored on iCloud (or iCloud Drive) like eg. a backup. Most of these should have been on by Default, probably Photos too.
iCloud Drive also has its own options, see below;
View attachment 37737
Occasionally I will put a document into iCloud drive on my MBP because I want to be able to access it on my iPhone/iPad. On those devices I will see those files in the Files App > iCloud Drive and on
the Apple website cloud.com when I login to my account.
Some 3rd party apps store data and sync across devices via iCloud Drive like my Password Manager. See below;
View attachment 37738
Note; Desktop & Documents Folder is
off. Do not turn this on unless you have a full understanding of the implications.
The other items are effectively backups and stored in iCloud Drive.
I hope that makes things clearer.
So, to answer your questions; if as suspect your Photos item is ticked in the iCloud list you can untick it without loosing any data on your devices (or iCloud).
As for; "I don't want to store stuff in iCloud Drive", you're not, if your settings are essentially like mine then you're just syncing via iCloud.