iMessage - deleting & preferences

My iMessages are taking up the majority of the hard drive space on my computer. I want to free up space on my MacBook Air.

If I change my iMessage preference on my MacBook to delete older messages (more than 30 days), will that impact ONLY my MacBook, or will it also (somehow) delete the older messages from my iCloud (and therefore, iPhone)?

Similarly, if I choose to not enable messages in iCloud on my MacBook, will that only impact the iMessages to/from the MacBook, or will it somehow impact the messages in the Cloud and my phone?

I think it will only affect the iMessages on my MacBook, but I want to confirm before I start deleting.

Thanks!