Hi,
Our plugin allow to redirect the registration from Joomla to HikaShop, so if you disable it it will use the common Joomla form.
To use the akeeba one, they have maybe a plugin for that, not sure.
When purchasing products on HikaShop, if they are not registered, they will be redirected to a registration form, as said previously the Joomla one, if Akeeba don't have redirection.
In your case, I think that the best way will be to use the integration we have with Akeeba subscription, use the HikaShop registration and create the 2 kind of payment options as HikaShop products.
These products will be related with two akeeba subscriptions. Restrict the other products to a specific user group, then on the "registration" products edition page select the corresponding akeeba subscription, set a value for the option set a user group after purchase.
Doing like this allow the customers to pay subscription products, and allow the access to the common products only if a registration one has been bought.
I hope this answer to your question. Here is documentation about our integration:
www.hikashop.com/support/support/documen...a-subscriptions.html