Expanding on what was discussed here: content-management-system-with-a-separate-publisher-server, after installing multiple publishers againstone CM environment, other than thread adjustments in the MMC snap-in are there any other ways to tune this type of publisher configuration (i.e. focusing one publisher for specific publications or ways to improve rendering times)?
You can, indeed, configure queue filtering so that your scale-out publisher only processes some items. For the most common use-cases, you probably don't want to do this - mostly it makes sense just to have an extra publisher picking up items in the normal order and generally helping to improve throughput.
If you don't mind having an under-utilised publisher, you might think in terms of dedicating one to high-priority tasks. You could even set up your publishing targets in a way that allowed you to prioritise one group of users over another. To be honest, though, I'd stick with just sharing the load evenly unless you have special reasons to do otherwise.
Don't forget that you can also scale out other services. For example, if you have a lot of automatic workflow activities, maybe you'd want to put the workflow service on a different machine.
The search service was always the tricky one. You could put it on a different machine, but then you'd have more work to do because the search collection could only be in one place. (I haven't looked at this since they went from Verity to Solr; perhaps it's easier now.)
I have a blog post on filtering/prioritizing publisher traffic here:
My advice, always leave at least one publisher monitoring the entire queue to ensure no items fall between the cracks of your rules.