For starters I dont always overline the rod only in certain circumstaces where short cast are required or when fishing a tree lined pool with no space for a back cast. I often use a shooting head set up for sea trout fishing at night so thatI dont have to false cast, shooting heads are just a short "overlined" length of line.Over lining a rod allows the rod to load with less line out of the tip, most beginners struggle at first to arealise a long line so this is a good way of them gaining confidence and also learning how to shoot line. Most beginners will benifit from going 1 line rating higher.I only fishwith the fly and dont use flying C's, spinning is for those that cant cast a fly. I live within 1/2 mile of a very good salmon and sea trout river and have access to many miles of fishing and to get into the best spots then sometimes you have to alter the way you fish / castthe fly.
Most of the 2 tone lines are for spey casting or shooting headswhere the head length is critical due to the line profile, with any more than 2m of overhang it is almost impossible to trasfer the energy down the running line and into the belly of the line. When fishing a WF or DT line the colour change is not needed as you should be able to feel what is going on.
Never seen a snap T done with a single hander, I find it to be a prety awful cast but it has its benifits when fishing with a double hander and a skagit set up or for those that cant perform a nice single spey.
As for my range of castI have enough to cover all circumstances, with the single hander overhead cast with and without the double haul, roll cast, sing and double spey. With the double hander single and double spey (left and right handed), snake roll, roll cast, jump roll snap T / snap C. And whilst on the subject of spey casting most spey lines do not meet the ATFM rating and are in fact heavier than a dt equivilant and therfore overlined for the rod.
When have the time tryto learn from those with more experience and an open mind. You stick to what the manufactures tell you, play safe and be a novice all your life. 90% of fish are caught by 10% of anglers I will let you saty with the majority!!