tRio has a "line out" setting under its "settings" menu allowing you to choose between either "fixed" or "variable" line-out volume.

In "fixed" mode, the line-out volume is fixed, but the amplified and headphone output can be adjusted via the wheel on the front panel or volume buttons on the remote.

In "variable" mode, all the outputs are adjusted via the wheel and remote.

The difference between tRio and the other clients is that with tRio you can change between these two modes via the menus. With the other clients you have to use a different receiver.arf (with a patch applied to it or not). And so it's less easy to switch.

But then you're not really going to need to switch that often. And so while it's easier with tRio, it's not a BIG DEAL.

Cheers
Paul