We'll integrate with it where possible when available. Most likely we'll simply release a Joomla plugin that integrates with it. Such plugin would be free, but not included with CB core since it isn't mandatory for every country or site.

You don't need any custom forms for consent requirement. The terms and condition fields are perfectly acceptable as means of obtaining consent. You can have as many terms and condition fields as you want as well so you can create the at least minimum 2 (site terms and privacy disclosure) necessary for GDPR compliance. You can add more as needed depending on what disclosures you need. It is also acceptable to put disclosures in field descriptions (e.g. if their email address is to be used for marketing you can add that to the email field description); several large name companies are already doing this (e.g. Microsoft).

The rest of the GDPR compliance is mostly on you at this point. If a user asks to be deleted then delete them. If a user asks for a data dump use CB Juice or export directly from phpmyadmin. If you want to automate user deletions use CB Privacy and its Delete Me field. CB Privacy will also eventually have an export feature to export their CB user data as well. This would officially mean all compliance could be automated.