Good questions.
1. It's personal preference. I like to mix a lot of DnB tracks, so I would use a BPM range that would encompass 175 BPM. It really boils down to the affect it has for listening to the metronome and for Quantized enabled options for Hot Cues, FX, etc.
2. "Normal" analysis is better for most modern-era music, Top 40, "EDM," etc. Music that is perfectly quantized that never strays from the tempo. Music crated prior to the DAW revolution was never perfectly in sync–multiple takes were often cut/combined using tape, so slight tempo variations–while not obvious when listening to the song, become painfully obvious when trying to beatgrid the track. Even older rap songs, while making use of classic drum machines, often experienced drifting tempos. So in cases of live music or music that was created prior to precision DAW editing, Dynamic analysis is your safest bet since it will compensate for changes in tempo.
Having said that, I prefer to play it extra safe–I import any questionable tracks with unsteady tempos in Ableton and take care of my Beatgridding in there. This guarantees that I fix the issue and makes mixing much easier since I don't have to constantly stroke the platter to compensate for the drifts.
Cheers.
