The Helios is a great little, under appreciated electronic variometer!
The Helios has two ports on the back, a Flarm port and a CAN port. The CAN port is ONLY for connecting the rear seat repeater to the front seat unit.
The Flarm port allows for the connection of an external GPS - IE Flarm at a Baudrate of 19200. It provides a reasonable Flarm Clock collision warning when the Flarm issues the warning. It also has the Flarm radar page. When connected to a GPS source (Flarm) the Helios will provide final glide and navigation back to the take-off point.
I do not believe that there is any way to connect both the Flarm and Oudie to the Helios. Connecting the Oudie to the Flarm port may allow GPS signal to be passed to the Helios from the Oudie, but I don't see any point in doing so.
It sounds like there is no Flarm currently installed in the glider. Given that you are starting from scratch, I would install the new Flarm Fusion. You can connect it to the Helios via the Flarm RJ ports on the two units and you can connect it to the Oudie using the bluetooth option on the Fusion and Oudie.
With the Oudie providing Flarm targets on the moving map and some warnings and the Helios providing the clock display, I would start with no other external display. If you find you want more Flarm details then adding a Flarm LED display or Flarmview or Traffic Square would be an easy addition.
http://foxonecorp.com/index.php/lx-navigation/flarm-display
http://foxonecorp.com/index.php/lx-nav/flarmled
http://foxonecorp.com/index.php/lx-nav/flarmview