In the G-Major, delay happens before Reverb. Reverb is the last effect in the chain... or parallel!
There are actually flexible routing options -- effects can be in series, like your pedals -- one after another and so on, or they can be run in parallel or semi-parallel, where the G-Major puts some effects in front of each other but others run next to each other, so for example the same dry signal goes to your delay and goes to your reverb instead of the delayed repeats going into the reverb.
You should download the user's manual from the TC Electronic web site and read up on it. You'll find it's quite flexible.
It also has a compressor built in. Wiring your setup provides for numerous options.
1. Get rid of the CE-20. TC makes the best sounding choruses out there.
2. If you really like compressing your signal up front, then leave the compressor at the front of your signal chain. In your effects loop, go into your DD-20 and then into the G-Major, then return from the G-Major back to the amp/preamp. It's not ideal. Really, you should get rid of the DD-20. It's a great delay, but you don't need it with the G-Major's delays. Or keep it and use it for special effects.
I don't really know anything about the koch pedaltone to comment on it.