First and foremost: You get what you pay for. I work in an industry where I get to see and compare all sorts of factory and aftermarket automotive parts and trust me, you get what you pay for. OEM is always quality and always fits. Aftermarket is cheap and it shows in both fit and finish. The exception is knowing what company actually makes certain parts for the factory and buying it through an aftermarket vendor. Example: Denso makes all sorts of under hood stuff for Toyota, Honda, Nissan, ETC. which are installed at the factory and sold new over the counter, but they remove the factory stamping and sell those parts at half the cost through the likes of Autozone, Oreilly and the website Rockauto. Motorcycle manufactures I'm sure do the same kind of thing. I'm fairly confident wheel bearings are outsourced to companies specializing in bearings, such as NSK and Timken, slap a Kawasaki sticker on it and eat your paycheck for dinner.
Now, on to your links. All Balls is a decent quality. Everything else is dirt cheap and don't be surprised if you wind up throwing it all in the trash in a fit of rage when you can't get them to fit right. Did that with an aftermarket petcock I got for my old XR600. Threw it in the trash where it belonged and promptly forked out the dough for a factory new petcock.
The one exception is the SS braided brake lines you linked. I don't think there's any cheap-o, low quality offerings on brake lines for the EX at this moment in time. You're probably safe with any one you buy. I've been running the cheapest one ebay had to offer (50 bucks), made by a company called Russel, for 3 years now and it works just fine. No signs of any of it falling apart or showing premature wear.
Before you go actually buy a brake caliper or master cylinder rebuild kit, make sure you actually need it. The seals can fail, but I have found that to be rather uncommon. I've got almost 2 dozen EX calipers in my garage and I don't think any of them leak and some are pretty nasty. Rather, I've found the actual metal more likely to wear out than the seals. At 100,000 miles, my original front caliper was getting rather scored inside the piston bores, but the original seals were still holding fine and looked good. The front master cylinder began leaking at 135,000 miles. A teardown revealed the failure to be the piston bore severely worn out and scored. Seal was intact. Granted, I'm changing my fluid at the factory intervals, which helps keep the seals healthy.
If your system is severely neglected, then the seals may need to be changed. However, if they're that bad, you may have corrosion issues in the aluminum calipers and the pistons may be pitted.
I'd say to cleanup up the calipers and master cylinders, put them back together with the original seals and see if it all works. It is important to note that getting the front master cylinder apart is a bit tricky. The dust boot likely won't make it out without getting a hole in it, so definitely at least order one of those.
1990 EX500 - 140,000 miles as of May 27th, 2019
1993 Ducati 900SS - The real canyon carver
2002 EX500 - Undergoing a full restoration