Can xposed framework impact system performance and battery?
Xposed isn't a separate service: instead, it's a wrapper in every process, which replaces some built-in functions from the Android framework.

For this reason, it's very likely that it'll have some effect on system performance, but exactly what effect depends on the particular modules. For example, it would be possible (but unlikely) for a module to replace a built-in function that's called frequently with a different version that runs more slowly and uses more battery (and probably even gives the wrong answer at the end).