Difference between Direct Routing, Group, and Send

I’m having trouble with a couple concepts:

Under what circumstance would I direct route to a parallel drum bus vs send to a parallel drum bus? Additionally, why would I direct route to a regular drums bus vs send to a drums group?

Lastly, what does the summing mode do exactly? The manual didn’t define it too much,

They do the same thing, but all a bit differently. I use direct routing for quick switching, and for temporary routing to hardware, or for printing stems. You cannot send level with direct routing, it is just switch (or split if in summing mode). Also there is no pre fader.
For parallel processing send level and pre fader can be handy, so you can use send to fx or send to group.

If you use direct route, you disconnect previous routing, so it is handy if you want to quickly reroute signal, but then you just switch it back when needed. It is like a switch. (Unless you use summing mode, then it is like a split, same signal goes to all outputs.)

Thanks! What does summing mode do??

Hm, I explained it above. Summing mode is like a signal splitter. It sends the same signal to multiple outputs at the same time.
If you have summing mode disabled, then selecting new direct output will disable previous one. But when you enable summing mode, then selecting other direct output will keep previous one enabled. So you can have 8 simultaneous direct outputs active in summing mode. Without summing mode you can have only one direct output active at the time.

It should really be called “Split Mode” instead of summing mode IMO.

I use the Direct Out to switch to my outboard/analog summing device at the mixing stage, while routing everything to the main out when tracking etc (some groups in between though).

I don’t use them in “summing mode” much, as I rather do the old school send/paralell bus processing/compression.

The Direct Out routing capability is a very nice addition I am happy got ported over from Nuendo (when that happened I went Cubase exclusively).

Are the output in the Pre rack and Direct Routing the same thing then? One just overrides the other?

This is my question as well
How can I setup the mixer to have all channels via the pre rack to main out, but at the same time have a mult to out ST2 to ST16?