1) They both have their pros and cons. Blitzers are harder to find a team that will use them properly.
2) Check their primaries. Speed above everything. More so on blitzers than coverage, which will also need a hefty dose of agi, vis , jmp.
3) LBs do not have a lot of useful SAs. I would focus on shed blocks (on both) and swat balls (on the coverage). Potentially diving tackle. A blitzer will want first step as bonus SA. A coverage guy might want super vision.
4) Too many choices that depend on exactly how your player actually is used. Can't help you here other than give you a huge list of possibilities or giving you my opinion which isn't considered a good idea by other people.
