Hi and welcome to the forum. The simple answer to your quesition (and you'll despise me for this) is, "It Depends".
It depends on the types of pads, product and even machine. I know when working with a typical DAT compound on a CCS Pad and my trusty PC7424xp, it's acceptable to "butter the pad".
When working with my Rupes System, usually 4 -5 pea to dime sized drops.
The other factor is the pad and the product work together as a system, if the pad gets bogged down with product, it may become ineffective at cutting. When I'm working, I want a balance of PAD and product working together. Typically I go for the 5 pea/dime size drops...
Another thing to consider is changing out your pads often. The general rule of thumb is 6 pads for cutting, 4 for polish, and 1-2 for finishing (LSP).
My last detail was straight out Microfiber Pads. If I used anything but pea sized drops I would have sling everywhere...
Try experimenting... If you do section passes and need more product, it's ok to re-apply product. Again, there are no hard and fast rules...
Many other members will chime in after this reply and offer opinions. You're opt to get more good advice...
Hope this helps.