Inter-changeable Tips....
I purchased an inter-changeable tip line a couple of years ago and decided that I'm not a fan. :x :x The ovenience of being able to readily change the tip is overcome by the overly thick, main section of line. It takes up too much space on the reel and takes more effort to cast due to the thick diameter of the line. :( :( Besides, what's the difference between changing a shooting head and a tip :?: :?:
Either ashooting head system or an integrated sink tip line is a better choice, IMHO. 8) 8) In answer to your question about sink tips, your choice should be dictated by your needs (....as mentioned in my prior post). If you're fishing deep, choose a fast sink rate. If fishing shallow, choose one with a slower sinkrate or a floater.
If you live in the Sacto area, go to Kiene's or your favortie fly shop and ask them to cast a demo rod/line. You'll be able to evaluate this stuff and meet your needs. :D :D :D
Research is always fun :) :)