Adding a new axolotl to my tank?

Hello! I'm a very new axolotl owner and have a GFP leucistic named Kimchi. (Unaware of gender since it's too early to tell, but let's just assume it's a "he") He is only a few months old and 2 inches in length.

I was considering adding a second axolotl to my tank, but I hear that young axolotls can sometimes have cannibalistic behaviour and I really wouldn't want things to come to that. Even if they don't cannibalize each other, they may attack each other and that is also something I'd want to avoid. My tank is a 20 gallon but it has a bump and staircase attached in its centre which I guess would make it smaller. I'm going to upgrade once Kimchi gets too big for it, and for the possible new axolotl! This new axolotl would be the same age as Kimchi and the same size, but a different variation.

I really would like to have him interact with another axolotl, and I find the species truly intriguing and amazing. Could I do it?

Here's a link with a bit of info about tankmates and putting axolotls together:
Axolotls - Requirements & Water Conditions in Captivity

I just put my two together in a 30 gal tank a few days ago. They're 6 inches long, I got them when they were 3 in. and kept them in separate 10 gal tanks. I was nervous and watched them closely after I put them together, but I haven't seen any sign of aggression or nipping. I made sure there were plenty of hiding spots for them, and I also ensure they're well fed. They tend to stay on their own side of the tank; the one time I saw them get face to face, one immediately turned tail and took off.

I was interested to read in the link above that wild type axolotls tend to be more aggressive, and they like to attack morphs (leucistic etc.). I want to get a wild type axie, but now I'm not so sure it would be a good idea. My two are GFP leucistic and GFP golden albino. The leucistics are cute with their little black eyes! Mine's starting to get tiny freckles on his nose.

When you do add a second axie, make sure you check the water parameters every day for a week or two. Adding another can cause toxins to increase until the tank bacteria grow enough to compensate.

Thank you so much! And I agree how leucistics are cute with their little black eyes