voice count shows how many users are in a particular topic.
for topics
you can edit the loop-single-topic.php file by copying it into your child theme and changing the voice count number code to whatever php tag you have from a plugin that has a specific template tag to show a posts like count.
change <?php bbp_topic_voice_count(); ?> with what you have.
to edit the label voice in the bbPress header you edit loop-topics.php and change <?php _e( 'Voices', 'bbpress' ); ?> and change it <?php _e( 'Likes', 'bbpress' ); ?>
for forums
its close to the same instead look for loop-forums.php and loop-single-forum.php
and the php code would be similar but instead of topic_ look for forum_