The answer to 1 is personal choice and the quality of roads in your area (i.e. will you be constantly bottoming out on speed humps and potholes?). The answer to 2 is generally yes, although if your lowered set-up is too stiff, it could impact handling adversely.
BTW a compliant ride and good handling are not mutually exclusive. I have Ohlins coilovers and the ride is silky smooth, but the handling is still a vast improvement on OEM MSport.
E92 pre-LCI 325i - Ohlins R&T; H&R spacers; M3 strut brace; Swift thrust sheets; BMS clutch stop; BMS CDV; RE g/box mounts; Saikoumichi OCC; K&N; Cyba scoops; BA diff brace; BMW Perf Exhaust; M3 rear spoiler; M3 white dash LEDs; LED Angels; LED side repeaters; BMW Perf black grille; CSL reps; SSDD carbon diffuser; Monster Wrap black roof