The title says it all: Are questions about best practices on-topic?
To give some context, I think that it is fair to ask the question in tex.stackexchange.com why the commonly cited best practice in TeX editing to split your document into sub-files for the chapters/sections is actually a best practice - I can think of 10s of good reasons for not doing so, but only of two for actually doing so. The question would list the reasons for either way as a starting point.
I believe that they might be on-topic as answers will consider valuable information for practitioners. They might be off-topic as the question is quite open-ended and it is probably not suitable to pick a "right" answer.