I would say, NoSlowAnimations would help with that. I'm currently working with a friend on speeding up his iPhone 4. Also, daily cleanup using iCleaner helps. Parallax isn't needed IMO, so Reduce Motion can be on (if it's even in iOS 7)
There's also some daemons I think still on iOS 7 that could help with RAM.
But from other users, iOS 7.1 betas weren't laggy. So, if he wanted a iPhone 4/iOS 7.1 jailbreak, he would needed beta 3 and find a way to eliminate the expiration, which there is a way.
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