Next year in summer I want to take part in my first triathlon.
The distances will be 400m-750m swimming / 20km cycling / 2-5km running.
For short course triathlon as you suggest it is not worth worrying this much about shoes.
Either use pedals with clips and straps (cages if you will) and ride in your running shoes, or else switch shoes in transition.
For your runners, they sell stretchy laces so you can slip the shoes on, no need to retie the laces.
This will minimize transition time.
Running shoes that are properly fit to you are way more important than anything else. You can ride a bike in sneakers or in road shoes, but you cannot run in improper shoes for very long.