Use iCloud as Photo Backup

First of all, sorry if this has been answered several times already but I have not been able to find the answer :-)

I am currently using an online backup service to keep a copy of my 50gb+ photo folders from my mac. These are photos taken with my old school camera and I only need them on my mac.

I am running out of space on my mac and would like to switch to iCloud as backup to utilize the 'optimize storage' on my mac. I know that will not remove the files from my mac but will reduce the disk usage. I guess that would be possible as long as I choose 200gb storage plan?

However, I do not need the pictures downloaded to my iPhone or iPad which are on the same iCloud account. Is that possible?

Feeling hopefull and waiting for your response :-)