Well... there's the good part and the bad part.
But let's start with the good part since that is just so much more cheerful.
Antergos is THE recommended Arch Linux derivative for UEFI systems
Like any Operating System, or OS for short, Antergos cannot mix. If you have Windows already installed in, say, Legacy mode (or any OS for that matter) it must be re-installed as a UEFI system for Antergos to work and vice versa.
This can be a deal breaker for some, but if you can successfully re-install your other OS(s) in UEFI mode, then this will really help you in the future since most Operating Systems are now moving to UEFI.
Hope this helps!