I like having a 90-degree valve stem, makes it easier to check air pressure and fill air.
I would not recommend using a tube too big, be that in diameter or size, because it can cause wrinkels that again can chafe against the inner walls of the tire that over time can lead to a blow-out. YMMV. Nor would I use a tube that is too small, because it will over-stretch and hence become weaker. Of course, in a pinch, one would fit whatever could take you home, but then with caution until the correct tube could be fitted.
Another preference is natural rubber tubes. They do have one downside compared to butyl tubes in that they do leak a little air all the time, requiring more frequent checking of air pressure. However, natural rubber rarely rupture when punctured, wheres butyl virtually always rupture. In case of a puncture, the natural rubber gives you more warning before going flat, whereas the butyl tend to deflate instantly, which can lead to a crash if unlucky.
