You might already know this, but I just found an easy way to have custom tooltips on inputfields:
$field = $this->modules->get('InputfieldSelect');
$field->name = "example";
$field->label = "Cool Tooltip";
$field->attr("uk-tooltip", "title: My tooltip text; pos:left; delay: 200"); // this line
$field->addOption("option1", "Option 1");
$field->addOption("option2", "Option 2");
Have a look here for all the options.