Should I let my two male canaries see each other in separate cages?

Ideally, the more space the better, and three birds should have a flight cage that is big enough for them to fly back and forth horizontally in (finches tend to like horizontal rather than vertical cages). You also want to make sure each bird has their own access to food, water, and bedding areas, with dividers such as perches or toys to break up the space and prevent fighting over territory. If you do introduce a new bird, make sure to keep him separated for a week first to prevent the spread of any illness, and to make sure he is healthy enough to be added to the flock before doing so.

Budgies are social animals. Just because they fight sometimes doesn't mean they hate each other. They often interact to enforce a social hierarchy. If you need to keep them separate, try letting them out at the same time to have periods of time together, although this could stimulating the re-establishment of their social standings. Good luck.

It might work, however once both pairs start breeding and raising young, that cage is going to get crowded fast. It is best to keep only one breeding pair per cage to avoid overcrowding, as well as any fighting over shared spaces such as food, water, nesting material, etc.

A breeding pair should be kept alone unless you have one male with two females. If you have two males, they may fight over the hen. The proper environment, nesting box and diet will be necessary for a successful breeding.

It is best to go with the cage that has the most horizontal flight space. Peaked cages are OK looks-wise, but make sure it is safe and feet and wings can't get caught where the edges meet. Avoid round shaped cages as well as it can sometimes stress birds out to not have a corner they can hide and relax in. Any cage should have enough room to move around a bit, have some toys for enrichment, and have a place to quietly rest aside from food and water locations.

When zebra finches are all white it is sometimes hard to tell if they are male or female as they won't have the characteristic cheek markings, beak coloration or tail patterns. The two pictured look like they could possibly both be female, but it is hard to tell due to the distance from the camera and the lack of markings present (males will sometimes still have darker cheek areas, a stripe on the cheek, or a darker red beak). Males will also sing almost constantly that sounds quite different than regular chirping, and will also "tail waggle" when they are wanting to/attempting to mate with a female. If none of your birds are doing this, it is possible they are all female. Both males and females will show interest in nests and will go in them to sleep at night even if they aren't raising babies. If one is being left out, you can add in another nest or sleeping area to see if it helps.

Birds, just like other pets, may develop preferences towards humans. Acclimate him gradually by sitting next to his cage for ever increasing periods of time. He may flutter about and move to the far side of the cage initially but will eventually calm down. Once he does, place your hand in the cage for ever increasing periods of time. Make no attempt to touch or hold him. He'll flutter about and complain again initially. Speak softly and move slowly. Use praise and small treats after each episode. You may get to the point where Ringo will perch on a finger or sing to you, but if not, do not despair. Be patient and continue working with him. Canaries aren't "cuddly" like cockatoos or other larger birds. (I have 2 African Greys that are almost 30. I have raised both. One loves me, the other has murder in her eyes whenever I approach to clean the cage or feed her. It is what it is).