Please be more specific about what you're wanting to change. You can freely specify whatever label you like for your terms and condition fields. Within the terms and conditions field under Parameters > Display you can adjust what type of terms the user is accepting. If you want to change or replace the "Accept TYPE" you'll need to override the language string TERMS_FIELD_ACCEPT_URL_CONDITIONS to change it for all fields or FIELD_FIELD-ID-HERE_TERMS_FIELD_ACCEPT_URL_CONDITIONS for field specific override. See the below on how to use language overrides in CB.

www.joomlapolis.com/blog/kyle/18701-language-overrides-have-arrived

Terms and Conditions fields are perfectly sufficient for GDPR. They can be used for privacy policies, data disclosure policies, etc.. as you can make as many as you want. Set them as required if the data collected is mandatory for your site to function.

It doesn't have to block the registration. It will only do so if it's marked required and yes you are permitted to deny them entry to the site if they don't accept the terms (block registration) if consent is required for the service being provided otherwise just don't make the field required. There does not have to be 2 boxes a single "I Agree" checkbox is sufficient. You're reading far too deep into this. They are not imposing design limitations on your site. Be clear what you're collecting and why then ask them to consent. Even input descriptions can be used as means of disclosure (to explain what the inputs information is used for; e.g. communications or advertisemenets, etc..). Several examples below.

www.econsultancy.com/blog/69253-gdpr-10-examples-of-best-practice-ux-for-obtaining-marketing-consent
www.econsultancy.com/blog/69256-gdpr-how-to-create-best-practice-privacy-notices-with-examples