this is another extension of this post.
My dilimmena is that I am ‘forced’ to pay for 2T icloud plan as my current icloud storage is around 300gb. I have around 1.7Tb of icloud space that I am paying every month but left idle.
How to I use this surplus storage space wisely and may be save some $$ on other cloud services? Is it even possible?
Don’t think of it as wasted space. Think of it as room to grow! 
(If you want to feel bad, think about all the insurance premiums for home, health, and car that are paid over a lifetime and, hopefully, not used.)
LOL, yes, I feel better now…
Get more stuff. Movies are a great space-waster.
Start a family, then share with spouse and kids.
I’ve read all your connected post about iCloud and I agree with @karlnyhus and this is how I also framed how I used iCloud. I never have to worry about space. I can store more of my stuff and I can shoot more photos and videos. You can also share the storage to family members making 2TB cheap.
You can also use iCloud as Dropbox replacement. iCloud allows you to share files to other users by sharing a link to a file.
Storing your photos in another storage like local hard drive or a different cloud storage requires additional work and expense. There is just too much friction not to use iCloud for photos and videos.
I can do full iCloud backups of all my devices. Ain’t ever gotta worry about not connecting my devices to a computer to do a local backup. If I am abroad and lost my devices, I can buy a new iPhone or iPad and download everything I needed back on.
I still do a local backup to my main computer at home once a week just in case though…
Keep in mind that when you use “Optimize Mac Storage” the “older files . . . stored only in iCloud” cannot be backed up.
I really believe the term “Optimize Mac Storage” is misleading and possibly even meaningless. Although I confess I can’t think of a better term. “Store Files Somewhere But Maybe Not Where You Think They Are” ?