Helo's have all sorts of issue that arise as forward flight speeds increase. You have localized mach issue on part of the rotor disk and zero air speed issues on other parts of the disk. If you do a quick analysis of vector lift you will see the heli will totally lose lift on one side and/or probably destroy blades on the other side as they mach tuck. Regardless, the result is a sudden roll and loss of lift. That exact thing has happened before to some military helis during speed trials.

As for larger props allowing slower flight, I'd have to agree under certain circumstances. A high pitch prop can become stalled at lower forward speeds. I can imagine a scenario where a high pich prop could not easily sustain the proper thrust required for slow speed flight because of stalled blades. This would be especially true around the stall point because thrust would vary greatly as the prop stalled and then unstalled and then stalled again, etc. The low pitch prop on the other hand would not be stalled and could easily maintain a constant low thrust level.

As for breaking, there is no doubt that larger diameter props and multi blade props brake well. Problem with the two blades is they produce more noise than three blades because the tip speed is higher on a two blade. This is why in pattern and IMAC, where both breaking and low noise is important, you will see 3 bladed props. Both pattern and IMAC ships are grossly overpowered so a little loss from a 3 bladed prop is no big deal. I personally opt for a large 2 blade and just control throttle to keep noise down.

Cheers