hmmm, from the picture id say A, what is that around the B hole? Tin? Is it leading somewhere on the other side? But you specify that there is only 2 A holes, thats way to little. No you should not have to insulate the screws. Thats why im asking about the B hole.
I saw from the back; they are leading to nowhere. Those holes are isolated.
It's logical, it should be 'B', 7 Screws and has grounding, typical screws for the board is insulated
like this, the gold one is for chassis