Thanks for your reply; I got it working like this (using acf/load_field to first check permissions and set a global var):
add_action ( 'admin_footer', 'check_ACF_permissions_button' );
function check_ACF_permissions_button($post) {
if ($GLOBALS['projectManager'] === false) {
?><script type="text/javascript">
jQuery('a[data-event="add-row"]').remove();
jQuery('a[data-event="remove-row"]').remove();
</script><?php
}
}