particular welding and forming skills
frames are often one of
hiten steel
6061 alloy
7005 alloy
cromoly steel
other exotic and expensive alloys, reynolds tubing, etc.
apart from hiten steel, they require very particular welding and forming skills. This is because bicycles are extremely strong for their weight and there is not much room for error.
26 & 700 c: wide choices, anything else, limited choices.
26, usually wider, with tread and lower pressure, 700c, the opposite, which is good for going fast.