I pay for a 200Gb icloud storage via my Mac. Can this be used for my phone too so as not to incur additional cost as my free 5Gb is almost used up

Yes, if you're logged into the same Apple ID, or if applicable, one in its Family Sharing group.

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iCloud storage isn’t tied to any particular device. It is tied to your AppleID and iCloud account. It goes along with whatever devices you use that iCloud account with.