I mean, technically anything should hit if it's a tech punish.
Yeah so about this, I messed around and found that it can punish them from any point of the screen if you dash after throwing them.
Forward Tech: Run under them, 6a into a combo, it should land everytime if you time it right. You have to begin the 6a once the opponent passes over you.
Neutral Tech: Dash and 6a into a combo, probably the easiest one of the 3 techs to punish.
Back Tech: In my opinion, the hardest of the 3. Essentially the same as punishing neutral tech, just harder.
I'm sure you can do more than just 6A for tech punish, but I don't feel like trying anything right now.