First of all, I'm not sure about the "first two buckets open" thing... is that just because you have a two-column list of accordions (not something I commonly see)? Can the user open just ONE side, or does triggering one trigger both to keep them in sync? Finally, do they stay open until explicitly closed or do they "toggle", closing others when you open a new one in a given column?
Now, I have no idea what the rest of your page or site looks like, and I know nothing about your wireframes, users, or use cases, so I can't say any of this with authority, of course, so take it all with a grain of salt.
My concern with the two column thing is this: if the goal in opening the first two together is to keep them looking even, you are going to constrain the amount of content that can be in there, or you have to code them to open the same amount regardless of content. Even then, if the idea is to keep them looking even, you will need to control the height and/or content of every panel, which does not necessarily seem like a winning strategy. Along with that, I think having TWO items open to start might be more ambiguous and confusing to people than just one or none. I think that the two-column approach, while it might work in wireframe and mockup, will look lopsided and out of sync in practice, or will put constraints on your content, which a wireframe should generally not do. I also think that the two-column set of accordions is uncommon enough that just having them in a two-column format may rob you of some of the usual affordance of accordion panels.
I think a one-column approach may be your best bet... it is fairly standard for a reason. If the concern is vertical space, why not simply give those headers less padding and stack them in one column of accordions? That way you also have the option of having one open (make sure it is your highest traffic one! test that) and not unbalancing the layout.
As for open or closed affecting the affordance of the controls... I'm not really sure that will make much difference. If you have a stack of accordion headers with a common icon for expand-collapse, people will figure out they need to click on one to open it. Once they do, they won't be confused any more.