iCloud & iCloud Photos · Online-only files and Optimize Mac Storage
Does making files online-only on my Mac affect my iPhone or other Macs?
Short answer: No. Online-only is per device: freeing a file's local copy on this Mac doesn't change it on your iPhone, iPad, other Macs or iCloud.com. Only deleting a file from iCloud Drive affects every device.
No. Online-only is decided separately on each device. Freeing a file's local copy on this Mac doesn't remove or change it on your iPhone, iPad, other Macs or iCloud.com — they keep whatever they had downloaded.
That's what makes it a safe way to save space: Storage Studio's Run Tuhi cloud step, Free up in Storage Profile and Finder's Remove Download only affect this Mac.
Deleting is different: a file deleted from iCloud Drive is deleted everywhere. See delete versus online-only.