You are on the right path for selecting Kernel 2.6 (experimental) for MIPSR2

However which type you need to install depends on yourself since the RT-N16 is able to install all of them. Read up on the different type of builds they have here http://tomatousb.org/doc:build-types

Personally, I would flash the Extras (Ext) edition or the VPN edition if I need the VPN function.