Just a little feedback: Incremental is good. That allows for partial recompilation. You also want to establish good compilation unit demarcation.

However wrt to query being different from signals, especially since you described it in terms of push/pull, the difference is not very clear. pull is basically your query, or you actively recompiling. push is handled when you take livereloading into account.

There is no real difference.

Now there are different algorithm to handle the graph traversal recomputations. If you want to do it once, I guess it needs to be depth ordered and you need to recompile level by level each compilation unit that changed. So that you visit only once.