Re FOI, yes, definitely, as they form part of the official record.
I am not in favour of informal/private meetings. It's a grey area and fraught with legislative complexities. In its basic form, it may not even be legal. I agree with Mrs A regarding the value of training/briefing sessions, but the challenge is always to prevent members from determining policy at such an event.
I took over a parish council that had always set the budget and precept at a private session in a member's home, to which only 50% plus one of the members of the council were invited. Invitations were issued on a seniority basis, so with minimal turnover, some people had served for more than ten years and never been involved. I haven't completely weaned them off this process, but it now includes any members who wish to attend and I take away a draft budget to present to the next public meeting to ensure that all of the necessary decisions are taken in public and fully minuted. The flip side to all of this is that five of the seven members of that council are regulars in the village pub, so these conversations take place in the normal course of village life anyway.