All mowers are not supposed to exceed 19,000 feet/min blade tip speed. So, a smaller blade is definitely turning a higher RPM than a longer blade...but they're basically rotating at the same speed measured at the bladetip.
Mulching thick/lush Spring grass is a real chore...even if you're mowing every 4th-5th day. There's always bagging, but side-discharging is a true blessing IMHO if your lawn is expansive. Fertilizing in the Spring is entirely unnecessary if done in the late Fall (late Oct). If you're putting down a pre-emergent (in March/April) - they can be purchased W/O fertilizer added...same with broadleaf weed control (mid-May).