DD-WRT to Tomato to DD-WRT

Hi, 

I've been lurking around but never message before. 

Testing VPN from Private Internet Access.

A little bit of a back story.. I had Kong Mod DD-WRT (chk file only) to test my connection and it worked ok. I wanted to test which firmware utilized the processer better for VPN connection.

I moved to Tomato without any issues however my speed is about 10% to 20% less.  i have instructions to move back to stock firmware.

My question is when I install the Kong Mod chk file from 

http://myopenrouter.com/download/dd-wrt-kong-mod-netgear-r7000-04-19-2016

Do I also need to download the latest bin file from here too?

http://www.desipro.de/ddwrt/K3-AC-Arm/

or the chk file the most up to date info?

There isn't any recent information online of how to install DD-WRT

Is DD-WRT different from Tomato where you need an inital file (chk) then the firmware (bin)?