Yes, if you purchase the AppThemes club standard and then wish to upgrade to AppThemes club developer at a later time, you can certainly do this.
To clarify, the ClassiPress, JobRoller, and Vantage themes all have only the PayPal payment gateway integrated by default, and at this time there are plugins available in the
AppThemes Marketplace which can allow 2checkout or authorize.net for Vantage (the FXtender pro plugin gives additional payment gateways for JobRoller). Fees may depend on what type of account you sign up for (based on my perusal of their site), I would suggest perhaps contacting
authorize.net for clarification of this.
We don't have a specific community theme at this time, all of our existing themes can be found on our
theme information page.
The AppThemes club package does not include add ons available from our marketplace. Thanks.