Hi Cobus, 

Thanks for the question.

You are correct in the fact that a 21 and 24 hybrid has the same loft as a 3 and 4 iron respectively; however, because a hybrid has a longer Std. length and typically uses a lighter graphite shaft, many people hit their hybrids further than the corresponding iron. With that said, many people use a 21 hybrid AND a 3 iron to fill the gaps at the top of the bag. 

As for the 19H Vs. 19F, there is not a standard difference in distance, it is all player dependent. 

Hopefully these suggestions will put you on the right track, but the best way to answer these questions is to see a local Titleist fitter.

Thanks, 

Bubba

In your case, the most useful addition of a hybrid would be to replace the 3iron.  Butch Harmon never wants to see a 3I in an amateur's bag.  The other common name being utility club, you can use in conditions like fairway bunkers and deeper rough.  Even chip or putt from deep rough next to the green.  Ways you can't use a 3 iron.

If you can consistently hit the 3I and keep the distance gap from your 4I, that differentiates you from most amateurs.  The rest of us replace irons we aren't consistent hitting with hybrids.  What other distance gaps do you have from 3I ro 5W to driver?  Do you need to fill a gap (3W and 19H?).