I'll take a crack at your questions.
-what does it mean to chase a ring?
"Chasing a ring" means drawing or scraping wood off the bow's back so that the entire back is made up of a single growth ring. In other words, you choose a growth ring and do not violate it (cut through it) over the bow's entire back. (Back, for clarity, is the side of the bow that faces away from you when you draw the bow).
-and what does it mean to remove a propeller?
"Removing a propeller" refers to removing twist in the stave, usually with heat. If a stave dries to fast or unevenly it can twist, and if this is more than 5-10 degrees most people usually heat the affected section of the stave and remove the twist by twisting in the opposite direction. If the wood cools while being counter-twisted, the twist usually goes away (after a fair amount of trial and error).
-what do tip overlays do?
Tip overlays can do a few things. First, if you have a shorter bow they can help to prevent the string from sliding off the limb tips when the short bow is drawn longer than 1/2 its length. In essence, they reduce effective string angle a little. Tip overlays can also strengthen the tips when you use very thin tips. Finally, tip overlays look nice (or can, if you do them right). I suspect this latter reason drives most people to use tip overlays.
-and i looked in the new mag today and saw a bow thats tiller made the lower limb bend alot more than the top. whats up with that?
Not a clue. Someone had an idea, and gave it a try...
Best,
-Eric