IInternational Development with Econ at Bath or Econ and International Econ at Notts?

Both degrees are definitely interetsign to me but ID isn't as concrete as econ w more econ like at notts. Bath is a better uni probably esp for econ and it is a degree with a grounding in econ. The notts course is also relatively new.

Notts and Bath are broadly equal for economics. The distinction here is that the Notts course is a proper full economics degree, whereas the Bath degree is much more of a dual honours degree, half social science half econ.

is a dual honours degree better than a proper full econ degree?

Better in terms of employment prospects. Like will they prefer someone with an econ degree from notts to a social sciences degree from Bath? I think the with econ part rlly helps here.

Based on the two courses alone tho which one would you choose overall?

Which one I would choose? Well, I work in macroeconomics/macrostrategy so naturally an economics degree is very important if not a necessity for my role. Therefore, I would obviously go for the Notts course.
But the point I was trying to make is that which course I would pick is dependent on what jobs I want to go into, not what you might be interested in. Therefore, it doesn't really matter which I would pick

Please could I ask which you would choose if it was Economics BSc at Bath, Exeter or Notts? And factoring in a placement year at the first two options. I want to leave as many doors open as possible as I’m currently unsure which path I would like to follow beyond the degree. Thank you.

I don't really understand what you're asking. If you're wanting to leave as many possible doors open career-wise, then given the vast majority of careers won't care about the course differences between these three and the unis are of broadly equal level generally, then my advice would be just to pick whichever you like most.
If you're asking within specific sectors and industries, then that's a slightly different question. But that's not really consistent with the 'keeping as many doors open as possible' idea which you asked about.

I’ve read, for example, that in the investment banking sector, Notts & Bath are considered mid tier and preferable to Exeter. If I don’t yet know which sector I would like to work in following my degree, I want to go to the university whose economics degree is generally most respected out of the three and I also wondered whether the placement year from Bath & Exeter would have any bearing on that view. Thank you.

I appreciate that, but ultimately it's not like there's one course which would be clearly more respected by every single employer/industry than the other two courses. So you'd either need to narrow down the focus, or accept a vague more generalised answer.
To answer the question I think you're trying to get at, for the vast vast majority of careers, these unis and courses will be seen as equivalent to one another. For economics-based careers after just an undergrad, I would say there's little in but maybe I'd lean towards Bath and Notts. For finance careers, I think Bath and Notts are considered a little ahead of Exeter so there may be some advantages to favouring these courses at the margin. I don't think there's any difference for consulting careers.
How the industrial placement aspects plays into this decision is difficult to say because IP's are really only as good as the IP you get traded off against the summer internship you could've done otherwise. Personally I think IP's are a good scheme to be a part of (again providing you get a good placement), and Bath is generally seen as having the best IP scheme and network. But again, its possible you might get no placement at all or maybe a poor one, whereas it's possible another could get a decent summer internship at Notts, or the reverse of this could be true. So there's no clear answer from my perspective and you can actually still do placements at Notts and summer internships at Bath/Exeter so it's not as binary as you lay out. But given this optionality, this sort of thinking probably lends itself more to Bath.
I do think there's a risk that applicants overestimate the career implications of going to one of these unis over the others. The key thing to consider is that the difference in quality of students within these courses (e.g. the distribution across all of Bath's econ students) is larger than the difference between the quality of students on these courses (e.g. Bath vs Notts vs Exeter). And when the between gap is bigger than the within gap, it suggests there's probably not a lot in it in terms of career implications from picking one course of the others, and that perhaps factors such as module selection, location, campus, etc should play a slightly greater role in your decision than normal.

It depends on what sort of industries/sectors/roles/jobs you think you might want to go into after university. Some will care, some won't, but without any detail I can't exactly give you much of an answer.