Is it okay to submit article to Journal B despite contacting editors of Journals A & C? I've been trying to find a suitable journal for my manuscript. There are many journals that seem to be acceptable homes for my paper, but their aims and scopes do not overlap with my paper 100%.

I've been asking editors of various journals whether they believe my paper is suitable for their journal by sending them the abstracts (which these journals encourage on their website).

A few editors have gotten back to me and a few have not,
But while waiting, I found a journal that seems like a better fit than the other journals, which we'll call Journal B. Suppose that Journal C's editor has yet to get back to me and Journal A's editor said to submit the paper so that they can get a closer look at it beyond the abstract. 

Assume that in this case, all the journals are relatively equal in impact factor.

Is it rude to submit to Journal B anyways even after contacting the editor of Journal A and not yet receiving a reply from the editor of Journal C?
I see no reason to delay. Editors are busy and sometimes take a while to respond, but that shouldn't block the author as long as you don't submit to multiple places simultaneously. Of course, if it has been less than a week or so, the editor might be a bit grumpy. 

However, consider which journal would be the best fit for the paper. This will help you determine whether it is worth it to you to delay. 

Note that any response from an editor wouldn't be a commitment to publish, but only encouragement to do so. You would still be free at that point in any case.