Buy running shoes with about a finger-width of space between the end of your longest toe and the end of the shoe. This will allow room for your feet to swell as you exercise, keeping you more comfortable throughout your run. Bike sizes vary depending on the measurement technique and other factors. That's the best way to know whether you'll be able to stand over the bike comfortably. If you're doing most of your running on trails, consider a trail-running shoe.
Trail runners can be more comfortable on varied terrain than a regular running shoe.
The answers will get your closer to your perfect ride. Steel makes a slightly heavier bike but absorbs road vibration better than aluminum. Aluminum is naturally more brittle than steel. Whether that matters for you depends on how much you ride, where you ride, and how much you notice those vibrations. The random number generator.