Yes, the more poundage (harder to pull) your bow has the faster your arrow will come out. You need to visit a Pro Shop and hang out here awhile. Learn what is safe and what is not.
I'd hand out here...not sure about the Pro Shop. Around here most Pro Shops can't even install a string...lol. In all honesty, you will learn more from the people on here.
not sure what release speed is...yes, increasing lbs increases speed but not as much as you'd think....for me, its only about 1 fps per/lb....your results may vary