I do a lot of hiking myself, and I would recommend to make the system as simple as possible. The reason why is you will be cold, have frozen hands, hungry, tired (sleepy, exhausted, no energy) when you are going to make camp. It also might be dark, cold and windy.
You also want a rope efficient system. You want to carry as little weight as possible when you might walk 10-30km a day for a week or a weekend. Up and downhill, through difficult terrain and weather. Some people break the handle off their toothbrush, just to save a couple of grams more. Or dry their toothpaste and calculate how much they're gonna use during the trip. You can get a lot of toothpaste for 1-2 meters of rope.
When tying up your tarp I would use only two knots. Two half hitches to attach the ridgeline to the tree. Instead of using a prusik (too difficult and slow to tie), I would use either a tautline hitch or a adjustable grip hitch to make the rope taut. I would use the same system to tie the guy lines. Two half hitches to one end and tautline hitch on the other to make the rope taut.
The (roundturn and) two half hitches is very fast, easy and rope efficient to tie. You can also tie it on the bight if you have too much rope. Tie it with a slip if it's cold, wet and windy, then your knot won't be too difficult to untie in the morning. If wanted, you can add one or two roundturns to make the hitch grip the tree better.
The tautline hitch and adjustable grip hitch don't add as much "grip strength" as the prusik, and you can't get the rope as taut as with the versatackle. But they are much simpler knots, you can tie them much faster and much easier to get right the first time. They make the rope taut enough (you don't need the tremendous strength of the versatackle for this purpose) and by adding more turns you can get more "grip strength".
Roundturn and two half hitches:
http://notableknotindex.webs.com/roundturntwohalfhitches.htmlTautline hitch:
http://www.netknots.com/rope_knots/tautline-hitch/ Or adjustable grip hitch:
http://www.hawaiilibrary.net/article/whebn0001464710/adjustable%20grip%20hitch