I'd only use original pads and discs from the brake manufacturer. If you upgrade your brakes it's best to upgrade the whole system, not just the pads. Overbuilt components with more metal and more surface would normally dissipate heat better, reducing the prospect of brake failure. Also, mechanical brakes are easier to inspect, maintain and fix. You won't see if your DOT fluid absorbed humidity or you won't notice a leak until the brake fails, but you will certainly see a broken cable.

If you're running a >30mph ebike, you probably want something larger than 160mm rotors and something heavier duty than XC disc brakes. I'd suggest some downhill gear, including DH forks, headset, bars, cranks, etc. Shimano has the Saint line: http://bike.shimano.com/content/sac-bike/en/home/components1...

Hope makes some nice DH brakes: http://www.hopetech.com/product/tech-3-v4/

Avid has the Code: https://dirtmountainbike.com/bike-reviews/brakes-gears/avid-...

And other manufacturers also make calipers with >=4-piston calipers.

Again for rotor size, 160mm is typically standard for XC, road bikes run 140mm usually, some "all mountain" bikes have 180mm fronts, and 200mm is typically seen only on DH/4x/trials/dirt jump bikes but likely what you want for a fast ebike.

All that said, competition-level road bikes generally hold up fine at speeds up to 60mph (and the riders hit those speeds going down hills) and their brakes work fine. You obviously don't just mash them, and the rim surface they're clenching matters a lot, as do the pads, but the tech works well and has worked for the past 100 years. Weight distribution and even application of both brakes help a lot.

Competition level road bikes are new and get used for max one Tour de France season, so chances of wearing the rim, or the calioer material are minimal. I doubt they even wear the pads too much.

For >750W e-bikes that go over 28 mph you'd normally need DH brake tech, 180 rotors at least. Shimano Saint Ice tech is good, Magura brakes are also top notch, even the lower end models. Avid Code looks rather flimsy and advertises low weight. I would avoid any calipers w/o metal bodies as it does not dissipate heat well. The Hope caliper looks especially good - lots if surface, lots of metal. The brakes and the steering are the last things to save weight on.