Here is my take on things. (Switch)
I use my 7 weight Switch a fair bit and it would be fair to say that I have tried one or two lines
I now use two lines pretty much all the time and they serve me well.
First is a Skagit that comes out when I want to chuck large weighted streamers. Its a specialist line and not the nicest to fish all day.
My second line is one of Mikes Switch lines (6/7). I use this perhaps 95% of the time now, and that is probably because it does everything I could ask it to do. Last night I was swinging small doubles for Sea Trout with it, using a snake roll or circle C cast.
I then put on a Sunray Shadow for Salmon and used a circle C to cast at 90 degrees to my position and stripped the fly back.
I later headed to the Don where I used it to swing various streamers on a sinking Polyleader setup using a double spey. As the wind dropped and the big Brownies came out, I did something I thought I would never do with it and that was over head cast a LARGE weighted streamer!!
I was asked twice last night what line I was using because it was going out "sweet". I am not a great caster but Mikes line has definitely helped me control my casts better and I am now fishing much more effectively.
I also have a 5 weight switch and I use a Beaulah Switch line on that. It wont over head cast at all, horrible and heavy. It will, however, roll out nymph rigs and indicators as well as small streamers and tiny doubles. I will be changing this line to one of Mikes soon
I have used shooting heads, both integral and separate head/running line, and they work, but they are not as versatile and tend to be a little "heavy" on landing.
So, in conclusion, a dedicated Switch line should allow you to do pretty much most things a Switch rod is good at. With a specialist line "Skagit" you can add to your repertoire such as digging out heavy tubes/flies.
If I had to go for one line only, it would be a dedicated Switch, and it would be another one of Mikes.
As for your heavier outfit, I used a Guideline RTG Multitip system for a while and it was great but I now have various lines to meet all conditions, from Skagit to fine tipped full lines. I would say my Rio AFS setup is used the most with various polyleaders to give me the depth if required.
However, I am no expert Salmon angler, there are others on here that are far better qualified to advise on that.