Latching on is definitely the best way to feed baby as more milk is extracted when baby feeds. Pumps are not as efficient as babies and will only extract a portion of what baby actually takes.
Since breastmilk supply is based on demand, you wouldn't want to be solely pumping as this could see your supply drop. Also in the early days it is best to latch on baby on demand rather than pump. Pump only when necessary, like if you need to build up expressed breastmilk stock if you're going back to work, or if you are feeling painfully engorged and need some relief. Otherwise pumping and latching on in the early days (if you are already having ample supply) can lead to oversupply, and then more engorgement.
If baby is feeding 3 hourly and for a short time, this is fine as some babies are efficient at the breast. My nb would feed only 5-10 minutes in the early weeks too. They will change over time and baby may start feeding more or less but just make sure they are getting plenty of wet nappies since what goes in must come out!
All the best!