If you get to pick the second case, then there are endless software or apps that will claim to be the best free Mac cleaner but they may not be immune to a number of threats present in the sea of the cyber world.
The other path that you can follow is a wise one where you utilize a Mac cleaner app or Mac cleaning software that will take up the responsibility for cleaning your digital debris that may have accumulated on your digital companion. In the first one, you stick to the inbuilt cleaner on your Mac which will do nothing but just transfer the clutter on your cloud storage making it more congested, and then eventually you will end up buying more storage. In this situation, you can choose to follow two different paths. No matter how much cloud storage you get for free, after a while you will have piles of cluttered data accumulated on your Mac. The best free Mac cleaner application or software in such a case comes as a life savior app. Cleaning Mac is a task and getting in each file to clean seems futile and tedious.