One more thing to know. Livebearer females can store the male's sperm. they can have a number of spans as a result. There is a saying that livebearer females are born pregnant due to their prolific fry producing abilities.
I had a pair of common swordtails in my first tank. This is what caused me to get my second tank. Later on I became interested in the Montezuma swords and I kept several strains for years. Despite the fact that they are known to stop spawning for a while and then resume, I had tons of fry. I had lots of live plants. This helped with the first spawn or two. But, as more spawns came, it was not the adults eating the fry, its was their older siblings. But the Montezuma have a rep as fry eaters.
if you want to use a breeder box get one that allows new fry to drop into a portion of the box where they are safe from predation. But as noddle pointed out, breeder boxes can be stressful. Bear in mind that you will still have to do water changes on the tanks. Have a plan for what happens in the breeder box when you do.
I will not use the net breeder boxes because of this. I have a number of the Marina (now Fluval) large breeder boxes. They are made of plastic and with a small air pump they circulate water from the tank through the box.
https://fluvalaquatics.com/ca/product/hang-on-breeding-box/
I got mine from kensfish.com
https://fluvalaquatics.com/ca/product/hang-on-breeding-box/ but they are available from many sources including Amazon.