Joining for Adlam drop caps

There are four possible permutations of joining behaviour when a drop cap appears. https://github.com/w3c/afrlreq/issues/4 shows one, but i'd like to be clear whether that is what is specifically required, or whether it's just what happened to be produced by the application that created the text.

I need to ask, since the CSS spec was recently changed to say that for cursive scripts the default effect produced would be: (a) use an isolated form for dropped character, (b) use a right-joining glyph for the character that follows it. The example in https://github.com/w3c/afrlreq/issues/4 doesn't match either of those, so it's important to clarify whether different rules need to be applied for Adlam.

Here are the 4 possibilities (the text doesn't make sense, i chose the first word to show clear shapes). Remember that there is no markup separating the first letter from the second, so in some cases the joining behaviour has to be inhibited by the application.

A. Non-joining + non-joining (this is my interpretation of the example in the other issue).

B. Non-joining + joining (the current CSS proposal)

C. Joining + non-joining (an unlikely choice, perhaps)

D. Joining + joining (like Uighur)

Which of the above would be the preferred approach for Adlam script text?

Start by reading the referenced afrlreq issue 4 and the CSS proposal described in this issue, then compare the four illustrated joining permutations. Determine which behavior is preferred for Adlam and record the resolved requirement; completion requires an agreed answer rather than a code change.