Listen to the melody's working area
Sing or hum the main phrase and locate its approximate range on the keyboard. Notice where the melody spends most of its time, not only its single highest note. Play your proposed chord voicings and listen for a top note that repeatedly competes with the singer. Sharing a register is not automatically wrong, but dense attacks in the same area can make the phrase harder to hear. The arrangement needs a clear relationship between the foreground melody and the supporting piano part.
Change spacing before adding volume
Try moving the right-hand voicing lower or higher, or remove one doubled note. Keep the bass separate enough that the harmony remains clear. You may find that a smaller chord leaves more room than a quieter version of a thick chord. During a busy vocal line, use sustained support and save a short moving figure for the gap afterward. Check the chord tones against your verified chart, but choose their register by ear. A diagram locates notes; it does not decide the best spacing for a particular singer.
Evaluate the balance from a recording
Record a verse with the voice and piano together, then listen away from the keyboard. Ask whether the words and phrase direction remain easy to follow. If you accompany someone else, invite them to describe where the piano helps and where it feels crowded. Make one adjustment at a time so you can hear its effect. Avoid solving every balance problem by playing almost inaudibly. A clear accompaniment can be confident and present while leaving intentional space. Its role is to support the melody's movement, not to fill every available register at every moment.