Hi Richard,
The only information I can add beyond the threads you have seen is in the following threads:
https://community.roonlabs.com/t/bit-resolution-impact-from-roon-volume-control/1456/2
My understanding based on the above is that Disable is best when you are content for some downstream analog or digital volume control to have full command of volume. When you use it you are telling Roon not to engage in any volume negotiation with gear further down the chain.
In contrast, Force Max has Roon send a use max volume command to the driver which is the most that Roon can do to ensure that downstream gear retains a bit-perfect stream through any downstream digital volume control and into the DAC chip. This might be convenient when your DAC has separate digital volume settings for different inputs (eg.USB or coax) and you want to ensure that whenever you use Roon you are defaulting to max volume regardless of prior volume setting for that input. How the driver and downstream gear actually implement that command, of course, is outside Roon’s control. Sometimes a max volume command may over ride a previous volume setting for a particular input, sometimes it may not. Sometimes it may disable downstream digital volume control, sometimes it may work differently.
The above is just my understanding of @brian in the threads above. Hopefully he can join in and explain why I’m a dunderhead if it is too far wrong !