1st to technique:
if you want to do stranded knitting, you do not necessarily need to knit English (as well). Check out my blog and the videos I made and linked there. Maybe that is along your lines:
I did also include links for English-only woven backside and for the philosopher's wool video using both techniques.
2nd to the scarf:
You can make 2 scarfs
and sew them together. That is possible.
You can also check into "double knitting
" (a technique producing 2 "right sides" of the fabric and makes it double thick). Then the colors would be reversed on one side to what they are like on the other side.
another option to hide the back side with the floats / woven strands would be, to make a closed cast-on edge, but then continue to work in the round
and cast off with a closed edge (in the same orientation) again.
That will make a tubular scarf with 2 "flat" ends (that can be just the cast on, or maybe a cuff / ribbing of some sort). By technique that may be a little easier than double knitting (if you are not used to that) and also makes a double thick scarf. It would, though, be a little more flexible than an acutal double knit multi-color scarf. It also would look the same on both sides - which can be an issue with motives, that depend on the color (like a red rose on green and a green rose on red background? Not so much...)
For patterns and "sampler" pieces... just check out other knitting in fair isle motives and chose what you like. There is no copy right issues for your personal use that you need to respect.
You also find a lot of free charts of such motives - and of course, you can invent them yourself and sample on happily.