Cap Feeder Output Rates specification should start with the real closure.
Output depends on the cap, not just the motor speed. Tall caps, nested caps, light caps and asymmetric closures can all reduce practical feed rate. The line should be specified around sustainable output rather than a one-off test speed.
For a better buying decision, the useful comparison is not only hopper size or headline speed. It is how the feeder behaves with your closure, how the capper receives the cap and how easy the line is to run after changeover.
The safest specification route is to start with real closures, target output, line photos and the exact point where the cap must be presented. That avoids choosing a feeder on a generic speed figure that does not match the cap or capper.