I usually use Objects to isolate functionality, like

object TextUtils

for instance, instead of just top level functions, as it is creating an instance, it should be using more memory than an old java static function. Do someone know if an object with only functions its a waste of memory when the functions could be top-level?

Technically it does "waste" memory. On a modern 64-Bit VM a plain object takes 16 bytes. If that is an issue for your application, I guess you can optimize it. But I don't think it's worth it.

If you really have memory problems, optimizing function-holding singletons into top level functions will clearly not be your first step