Keep in mind that this is just my hypothetical, because no one has innovated RTwP in some time.
Casting a prepared spell in 5e takes about a second - think of how it plays out narratively at the table; sorcerer begins chanting and making movements with his hands, eldritch patterns glowing in the air around him; this is your queue to counter spell.
RTwP is a more narrative presentation of combat. When you see the sorcerer casting the spell, you pause and cast counter spell manually.
How will counterspell work in single player turn based? will the game stop and prompt each time?
