We're doing the same, 2 sets. Want wood but have been told they "may" warp, even though under a covered alfresco. Don't have a firm cost yet but indication from builder is $10-15k more than powder coated aluminium. Total width of each set is 3250 divided into 3 doors, with stacking security screens. Don't have a price for the aluminium ones yet to compare but +$10-15k has probably helped with the decision. Have bifolds at current house but will be going for stackers at the reno house because they can have the stacking security screens, whereas bifolds are difficult to security screen, you can flyscreen but it's quite a flimsy arrangement.

I think your house could be lovely with a bit of spit and polish! As per the previous comment, a paint job would do wonders. Our house is similar in that the ground floor is brick and the top is (now) weatherboard (over fibro). We lived in the old fibro for years before we could afford to renovate. It gave us more of an idea of what we would ultimately like. Here is our before and after. As you can see, we added a deck and changed part of the the roofline too.

Fly screens can be included. The track is wider to accommodate two sets of sliding doors, one your glass, the other your fly screen. Another option could be a retractable fly screen. This allows when the doors are completely open (no bugs around) the fly screen can be retracted completely to side of window frame.

Consider your household, and who will be using the door. I am assuming you will be getting a pool safety fence between the door and the pool. Tall bi-fold doors can be heavy for kids (and some small adults) to use. The sliding doors are probably the easiest to open and close if you are going to be in and out a lot. Bi-fold doors can crush little fingers if a child tries to close the door from the hinge point. Consider how much of the outlook you will be loosing with the frame for each of your bi-fold panels. With a sliding door you only have one interruption of the view if you have one fixed panel and one sliding panel. You may also like to consider flyscreening and the costs. Flyscreening a bi-fold door is much more expensive with the sideways retracting flyscreens, than a standard sliding flyscreen for a sliding door. I am not sure if you can retrofit a flyscreen to a bi-fold door in a a neat and tidy manner. Cheapest option would be no flyscreening! Bi-fold doors look spectacular for a photoshoot when they are fully open (with no flyscreening), but for day-to day practicality I don't think you can beat the ease of a large glazed sliding door, which will give you a better view of your nice aspect on those days when it is closed. Best of luck, Dr Retro of Dr Retro House Calls