If you love the look of white Venetian blinds, maybe you should consider a PVC blind that can be taken down and literally hosed clean? I grew up on a farm with plenty of dust from the gravel tracks and know I would've liked the easy clean option!

I got plantation shutters in my bathroom because my window is in the shower. Then I decided to get them in all my rooms. Wynstan do cedar on the larger wide windows over 70cm I have one window 1m wide. They say the pvc bows after a while so they recommend cedar. They're painted white and they do all look exactly the same. However I'd say the cedar feels nicer due to its weight, you can feel the quality. I rarely open the windows and its more for privacy, distributing the light than air flow. But they are also great because you can open the window and get both air flow and privacy with shutters.

I would definitely recommend three panels for the first window and two for the second in this instance. It will look far more consistent from the exterior of your home. We always match the configuration with the frames and mullions where possible for a neat finish. You can have each panel hinged individually, or have a bifold scenario... both would be acceptable solutions. You may have been recommended choosing a 4-panel configuration based on the type of shutters that particular retailer was quoting on. Different materials (timber, PVC, aluminium, etc) have different weight, and therefore different parameters for the maximum panel size. PVC is far heavier than timber or aluminium and can put strain on the hinges over a large expanse, causing them to sag slightly. The timber we use is Poplar - a forestry certified hardwood which is very lightweight and allows a lot of room for adjustment onsite (it's common for windows in older homes to be a little out of square because of movement over the years.) Timber can be made in larger panels than PVC, so your 2-pane window wouldn't be an issue.

@Kate @oklouise and @Julie Herbert thank you each of you for your suggestions. I was thinking about a venetian inside the shower myself as a temporary fix until the budget allows for something else. I figured if I even get a few years' worth of use out of it that'll be enough to get me to a more permanent solution - the idea of the personal courtyard is also very tempting and I didn't think about screens but another great suggestion. Thanks everyone for replying - I started off feeling very upset about my options and now feel very positive/enthusiastic thanks to all of the great ideas :)