External Hardrive / iCloud question

Hello, hope this is in the right place but I really need some help.

My Macbook Pro has now maxed out on memory (250gb). I've bought an external hardrive to move everything across but I have two questions I can't seem to find the answer for:

1. When I move everything across, can iCloud still sync to it to update? I can't find anywhere to help me do this

2. When all my files are moved off my Mac, will iCloud start deleting them on the cloud as they can no longer be seen on my computer?

Hope that makes sense, please help!

Thanks,

Iain