Removing iMessage storage on one device without it removing it on multiple devices

I have an iPad mini 64GB, iPad Pro 256GB, and an iPhone 15 512GB. I have iMessage sync turned on, so all devices are synced up. I'm out of storage on my iPad Mini in order to update to the latest software. My iMessages on my iPad Mini are taking up a significant amount of that storage. I'm aware that if I delete a message on one device, it'll delete them across multiple devices - which I don't want to happen. I only want to remove the necessary amount of iMessages on my iPad Mini in order to make room for this update. Is that possible?

It seems that I may be able to do this by going to Settings>Messages>Message History and turning Keep Messages to "30Days" instead of "Forever." My main question is that if I do this, will it remove messages older than 30 days from my iPad Mini? If so, will it also remove them from all of my devices?