Like the last poster said make sure the opening is the proper width to fit a pre hung unit. Like he said prehung units that big are a lot easier to move with the doors removed. Mdf Doors wiegh a ton and 2 of them in the frame would be impossible to move. A frame can be jockeyed around a tight stairwell. There is another route if the openings are a non standard size, bypass doors. All the closets in the bedrooms have them and I just ordered door blanks and installed them on new hardware. I recomend Johnson hardware for bypass doors. It's cheaper to order from the company than have a big box order it in. Here is a link that might be useful: johnson hardware

The roller type has to have some rattle or there would be too much friction on the wheel (it needs clearance on one side of the wheel). Also, since the doors are only supported on one side (and are very light) that flimsy feel is going to be there, for the most part. Best advice is to make sure everything is level and plumb (including making sure the floor bracket is plumb front to back). It sometimes helps to put a pair of knobs or handles on the door instead of just the one provided. Alternatively, maybe you would prefer a pair of opposing doors, such as separating those bifolds and installing each on it's own set of hinges? It's been done before. Not too difficult if both sides are plumb. If you have drywall on the sides, then first install a jamb set on both sides and top, then install doors (Stanley had some surface mount hinges that will do the trick), then door stops around (or at least at the top), and finally ball catches at the top. No more rattle!

You need to size the doors based on the hardware you end up buying. Chose they type of hardward and click on "click here for details" to see how to size the doors. Here is a link that might be useful: Johnson Bifold Hardware

Got a bid from Marvin doors $17k (Wood) and Panoramic Doors (Vinyl) $10k for a 10’ by 8’ door. Panoramic doors have 10 year warranty and customer service so far has been amazing! Seeing the Marvin door in person I was extremely unimpressed especially for the price. I like the fact that it was explained that Panoramic doors carry the weight at the bottom not the top. I was originally concerned about overall structure with such a large door. I’m finding it hard to reach anyone at Nana wall and getting a quote online is a pain.