This is normal behavior. There is much more to the JVMs memory usage beyond what’s allocated to the heap - there are other memory regions as well. There are additional tuning options for them, but it’s a complicated subject and if you aren’t actually encountering out of memory issues you have to ask if this is worth the effort to tune it.
Arch is not harder to maintain nor is it easier to break, that’s a myth. If anything, it’s the opposite, as a rolling release stays up to date, though it relies on the user keeping it up to date. If you get lazy with updates, then yes, you are going to have problems eventually.