Hi bass man,
I think you may be a bit confused about the difference of the WF and DT fly lines. I have listed the measurements in the tables and you can compare the measurements on the photos. There is one mistake in the WF diagram. It shows the Front Taper 1 as 7' 6" and I believe the correct measurement is 7'.
Tapered Fly Lines are designed for the line to unroll during the cast and the heavier, larger diameter line, rolls over and carries the lighter line forward. The final completing of the unrolling of the fly line results in the heavier fly line tip causing the leader to unroll like the fly line did. That is why the leader butt must be close to the size of the fly line tip. If the leader butt is too small compared to the fly line tip, the leader will hinge or collapse. The tapering of the fly line and leader results in more line or leader that you can cast. A level leader or fly line will collapse from its on weight and consequently you can't cast as long of a level leader or fly line as you can a tapered leader or fly line.
If you compare the running line of the WF fly line and the Belly portion of the DT line you will see that the DT line is much heavier in diameter. The larger diameter belly line of the DT fly line will limit the distance you can overhead cast a DT line. Up to some distance the level belly of the DT will assist in Roll casting. Eventually the the DT roll cast may also collapse from the shear weight of the belly line and the inability to impart enough energy by the caster to roll over the line.
You can see that the total head of the WF line is 46.5'. A good distance caster could carry most of that in the air and then shoot additional line on the cast delivery. The weight of the head will pull the light running line along and you can end up with an exceptional long cast. The long taper of the RIO LT line is not necessarily designed for distance but to enable excellent line mends. This WF line will also roll cast well up to 45' or so. Many Fly Fishers prefer the DT line for its excellent ability to roll cast and mend. If you make short cast a DT may help load the rod with less line out the tip.
You will find that different types of fly lines have many different tapers depending on what your target fish may be and how or where you are fishing. If you spend some time studying different fly line diagrams you will learn a lot about fly line design. Casting a fly line is all about energy. The rod imparts energy to the fly line and the unrolling of the fly line imparts energy down the fly line to the leader and then down the leader as it unrolls eventually delivering the fly to the water.
I just noticed that I didn't answer all of your questions. Shooting line is a light line added to the back of a shooting line like MP mentioned. The shooting line is lighter weight and of a different material than the shooting head. In the old days we use mono for shooting line but there are other options available now. I think you have the WF and DT fly lines mixed up. The WF im most cases will out cast a DT fly line. The first 30' of the WF and DT fly lines can be very similar according to the line manufacture design. It is usually after the first 30' that you start seeing the difference between the WF and DT fly lines.
Frank
Comparison of RIO LT Trout WF/DT Fly Line
WF Line Specifications | Spec
Line Size |5wt
Running Line|43.5
Back Taper |5
Body 1|22
Front Taper 2|12
Front Taper 1|7
Tip|0.5
Head |46.5
Line Total |90
30ft Wt. |140
All measurements are in feet.
DT Line Specifications | Spec
Line Size |5wt
Tip |0.5
Rear Taper |9
Rear Taper 2 |11.5
Body 1 |8
Body 2 |32
Body 3 |8
Front Taper 2 |11.5
Front Taper 1 |9
Tip |0.5
Line Total |90
30ft Wt. |140
