Hi Gordon.

Please look at this posting, that I wrote some years ago:

https://forum.rme-audio.de/viewtopic.php?id=34394

It contains useful information about the basic concept of TotalMix routing and recommended information resources.

The operating concept of TotalMix FX is actually "quite simple".

It supports you—among other things—to get an optimum routing for monitoring your audio.
So that not everything needs to be routed through the DAW (with higher latency over USB etc).
You can route audio for some use cases with less latency directly from an input to an output.
Any combination is possible:
audio from inputs and/or from the PC (top and middle row in TM FX)  to any Output (Bottom Row in TM FX).

Let me try to summarize the essential information in simple sentences:

Each output has its own submix.

You can configure what you want to hear at each output:
  Option A) Either audio from the hardware inputs (faders in the top row of TotalMix) or
  Option B) Audio from the PC (faders in the middle row).

The metering helps you see where an audio signal is coming from that you might want to hear at that output.

All you have to do is to
— click on an HW Output in TM bottom row
— move the fader of top and middle row (inputs and audio from PC)
to create the needed submix for *** this particular output ****

Do this for every output, where you need a special submix (monitors, headphones, …).

The rest is just the usual daily operation that you need to learn step by step.

Here are just two examples:

a) Bringing active monitors and headphones into the Control Room via the "Assign" function so that Control Room functions are available for your monitoring (e.g., DIM, etc.).
b) Saving your most frequently used routings, such as routing audio to active monitors or headphones. These are the 8 snapshots "slots" on the right side for saving and recalling the routings.

You should make backups of your settings to your computer using TM FX -> Save Workspace As ...

There are various reasons for audio drops and this is a topic of its own.
Especially VSTi can be CPU intensive, did you ensure to use high enough buffer settings in the application or DAW?
You need to balance buffer settings and latency.
The higher the buffers the lower the likeliness for audio loss, but the higher the latency.

But Apple also had issues in the past with audio drops, but this is something which is difficult to summarize in a few sentences. And the root cause in your case can also be another one. First I would try to adjust the buffer for audio as I suggested to find the sweetspot between safety and latency.

No matter how and what you write, people should realize that it takes some time to learn new things.

There is already enough information that gives you an intro and points you to useful sources of information.
Whatever you or me try to explain "the most important is this or that ... ".

The *really* important thing is to take the needed time and to read the available information to build up knowledge.

Olli, you, others and me wrote already so many times about TM FX and answered questions...

The sticky posting which I wrote some time ago was an attempt to give everybody a good guidance and pre-briefing what the objective is and where to find good source of information.

Every so often it appears to me that people think, that it is not necessary to read information, be it manual/text or video and have the expectation that everything has to be easy and self explaining.
But this is not the case. You need to learn the stuff like every other thing in life.