Mostly, yes — Mole primarily frees up disk space.
In general, junk on disk doesn’t slow down a healthy macOS system by itself. Where people sometimes notice a difference is indirect: bloated or stale caches can make apps do extra work, and very low free disk space can increase I/O pressure. Clearing outdated temp data can also force apps to rebuild fresh state.
Mole isn’t a performance tool. Any speedup people notice is situational and indirect, not a guarantee.