How long would be recommended to let them soak in water before giving it to the fish?

at least 2 minutes

What i do is simply to soak them in water, do some of my morning chores...then come back after. I dont take note how long they've been soaked, for as long as they're big and soft

Same here, I soak them while I get on with other things and then poar them in. Can be anything from 5 mins to 30 mins. You can try leaving for a while and see how big the pellets swell.

I soak them for about 5 minutes. They are as big and swollen as they are gonna get within 5 minutes that I find.

I use a mix of 3 kinds of pellets, Hikari oranda gold, biogold, and Wardley pellets. I will let them soak at least 30 minutes, sometimes longer. That way they are soft enough for my guys to eat easily and any pellets that are still floating can be gently pinched to make them sink.

I have a question that goes hand in hand with this topic.

When I used to have goldfish, I would soak my pellets for a bit (probably 1-3 minutes but I can't remember) until they were mostly soft. I would pinch them tight to get rid of air and compress they so they didn't make such a mess in the tank. Would this pinching method compensate for a shorter soaking?

I've never soaked flakes before because they don't expand so much. If you are feeding them to fancy goldfish, try to sink them below the surface before they get to the flakes so the fish can avoid gulping air.