Question About Oki/Tech Traps

Hi everyone! Maybe this question was made a lot of times and it's a basic mechanic, but I've doubt about oki/tech traps.
I'm a Soul Calibur player and a noob VF player (I started to play in 2012 but without a real experience) both games has similarities (a few ones) but in the oki/tech traps VF is a complete new universe.
In SC if you do a combo you can guess if your opponent will do a Ukemi, then you input a move (generally a mid/low horizontal one) and catch your opponent, the damage will be added to the initial combo damage.
In VF I watched some fights where, for example, Wolf or Goh can throw the opponent with a low throw after a successful ukemi, Taka can do a 2K+G after a simple combo like K+G P 1PP 33P+K and it'll generate a stagger state on the opponent and take can do P+K as a starter combo. But sometimes this attacks doesn't connect.
How does the ukemi traps works? Can all characters do it? is it a 50/50 mechanic?

Thanks to everyone for your time and help! I've a lot of more questions

 

I'm very sorry for the laaaaate reply (so much work), but thanks for your help. I was training your suggestion but there is something I missed, you have to guess if the opponent will do a ukemi, right? but also do you need to guess if the opponent will finish his ukemi with a standing or crouch block?
I mean, again with a Taka example, if I guess the opponent will do an ukemi, my next move could be 4P+K P if the opponent will be in a crouch block state after the ukemi or 2K+G if he finished the ukemi in a standing position.
I've this doubt because in Soul Calibur you only must guess the ukemi, the next move (a low or middle move) will connect for sure.
Again, thank you so much for your help