Will the Atomic Pi run the OpenWrt firmware?
It's an x86 board so I don't see why not
If it is an EFI-only BIOS, then it will need https://github.com/openwrt/openwrt/pull/1968 applied.
Edit: Support for its RT5572 wireless should be examined, if you desire to use wireless. Many wireless chips intended for USB dongles or on-board client use are poorly supported for 5 GHz use or for AP use, if at all.
Is there a easier way to switch atomic pi's single ethernet port from lan to wan and back again much like the gl.inet ar300m lite with its single ethernet port and software switch from gl.inet webui?