Is it possible to have Channels running on two computers and use one for internal and the other for external use or will this cause problem with the port forward of 8089 which I cant find anywhere to change.from the default
Yes, but they will have separate recordings, passes, etc. Also, if you are using OTA tuners, they will be shared between both DVRs. Remote access can only be enabled for one DVR, so any maintenance on your "local" DVR must be done from within your LAN. You will also want to disable Bonjour on the "remote" DVR so your local clients will not get confused.
No. Just forward the port to your "remote" DVR.
Ok
Thanks
If I priorities my tuners for each setup, shouldn’t that take care of any issues for local clients occupying the remote setup.
Or maybe just disable the tuner that should not be available in each setup.
May I ask what is prompting you to have an internal vs. external DVR server? Are you wanting to segment recordings/library? The server is very flexible and, depending on your hardware, be able to handle both internal and external clients easily, so it's a rather unique situation I would think to need to have 2 different servers running. But you know your needs, so ignore me. 
I am having issues with buffering external. I can not figure out if it is due to hardware limitations of the server or other things are at play here. So just to test and rule out this possibility I wanted to setup another server for external use only.
Gotcha. I had 2 servers running internally for a few months as I was migrating and testing.
Good luck, troubleshooting can be interesting in identifying the root cause.