You can run you Langstroth for wax by doing crush and strain for harvest (use foundationless or wax foundation). You can run a top bar hive for honey by extracting (You may want to plan what size top bars and what extractor). If you want both, you may as well just do crush and strain. You really won't get that much wax anyway even if you harvest it all this way.
The object of a Top Bar Hive (TBH) is to be easy and cheap to construct, easy to work (less lifting) and having natural sized cells. You can get the natural sized cells with a Langstroth as well.
Why a top bar hive? Why not a top bar hive?
It seems a lot of people get into top bar hives with a lot of misconceptions. They seem to think that a top bar hive is “natural” and there is no other way to have a natural hive of bees. I’m not exactly sure where this comes from, but I suppose part of it is that a typical top bar hive has natural comb and a typical Langstroth hive has foundation. But I have seen top bar hives done with foundation, and I have thousands of foundationless frames in Langstroth hives. So if your only reason for going with a top bar hive is to get natural comb, you have other alternatives.
Another is the belief that the shape is more natural. I’d have to say any shape is natural. I’ve seen bees in soffits, gas tanks, walls of houses, floors of houses… bees aren’t particular about the shape. I see nothing more or less natural about a top bar hive.
Another is that you want a horizontal hive. But you can build a horizontal Langstroth hive. I have a few and they do just as well as the top bar hives.
I think the real reason for a top bar hive is that you can build it from scraps for next to nothing AND you get the above benefits, to wit: natural comb, (with both natural cell size and clean chemical free wax) no boxes to lift (horizontal). If you want all of these in one combination, then a top bar hive is for you.
Reasons you might not want a top bar hive.
A top bar hive, because it has a limited and fairly constant space, requires more frequent interventions to manage it well. This is not a problem when it’s in your back yard and you can’t wait to get into the hive. But it’s very inconvenient if it’s somewhere further away where you have to drive there.