What is the easiest to use router that supports OpenVPN? Something that's getting software updates well? We don't even care about WiFi, we will be turning it off.
go for a DD-WRT: v24 Build 13309 or newer
Supported builds: OpenVPN, Big, Mega, Giga
Make sure that it should have to have 8 MB FLASH MEMORY for OpenVPN to be installed
You can also go for an Assus router that has the option of OpenVPN