Japa mala is useful initially. It helps us to increase concentration. It is like a 3-wheeled cycle. you have to chant the mantra and move the beads. It helps you to extend the time you spend.
Japa without japa mala, is for advanced meditators, who can atleast sit for meditation at a stretch for 45 mins, preferably for 3 hours. It is like a 2-wheeled cycle. initially. Here there is only oone thing to be aware of i.e. japa mantra. initially, you have to chant verbly, than mentally and than later on just try to be aware of the japa mantra. You are seperate from the japa mantra. you are not the mantra. You can go one step ahead in this japa by trying to be aware of the source from where the mantra is originating.
Sri Ramakrishna said " by hearing a sound of waves of ocean, one can follow the sound and reach the ocean shore".
So the origin of the mantra is the heart or the SELF or God or silence, whatever you call it.
In japa with japa mala, you cannot be aware of the origin of the source as some Â awareness is still in the physical body (since you need to move the beads even if you do not count them)
That does not mean that japa with japa mala is useless. You can be aware of the mantra if you have recited it for a long time by continous practice. japa with japa mala is a platform (specially for the ones who chant the name of any one form of God e.g. lord Rama). Afterwards you can drop the mala. but in the begining, japa mala helps.
But for some people, it is posible that they do not need to use mala from the begining. specially for non-dualists.