Hi,
You have to make a translation override on the key "X_ITEMS_IN_STOCK", regarding the "out of stock" it's already displayed by default.
www.hikashop.com/support/faq.html#tran
Actually we cannot select the variants with stock by default in the dropdown, it will require custom code.
What can be done is selecting another way to display the variants in the configuration, I think that display in table can be the alternative. By this way the customers will see all the variants and their stock on one page.