Length and angle of stem a real area of personal preference.
On the rise/dip front, if you are gonna be on the bike for long periods you dont want a highly agressive (i.e really low bars) riding position... go for sit up and begability for more comfort... But obviously less aero so trade off depending on what you want.
Length should only really be dependant on your bike sizing, but here trial and error come into play.
Some people seem to hate long stems as they make bike a bit (although barely) less stable and low speed weaving can be a tiny bit less responsive... but really it makes sod all difference
Length and angle of stem a real area of personal preference.
On the rise/dip front, if you are gonna be on the bike for long periods you dont want a highly agressive (i.e really low bars) riding position... go for sit up and begability for more comfort... But obviously less aero so trade off depending on what you want.
Length should only really be dependant on your bike sizing, but here trial and error come into play.
Some people seem to hate long stems as they make bike a bit (although barely) less stable and low speed weaving can be a tiny bit less responsive... but really it makes sod all difference