What is the best way to test if these CBSubs variables work correctly?

Create a Dummy gateway for testing purposes so you don't need to deal with exchange of money or and the test will be instant. Next be sure debug mode and maximum error reporting are enabled in Joomla global configuration. Then enable Debug under the Parameters tab of your action so if your conditions fail it'll output a var_dump of which failed and what they tried to compare.

How do I make the subscription to expire to test the CB Actions on expiration?

Expiring by any means will trigger that. This means simply cancelling it from the subscriptions tab will trigger the Plan Expired usecase.

How do make the auto renewal to happen so I can check the CB actions on auto renewal?
and same with manual renewal.

You should be able to just renew it manually from the subscription tab instead of waiting for auto recurring payment.