An Elements subscription includes full access to any theme listed here: https://elements.envato.com/wordpress
Other ThemeForest themes will not be included - Elements and ThemeForest feature some of the same content, but there are many more items available only on ThemeForest.
If you licence an item for a specific use during your subscription, you can continue using the item for that purpose after cancelling your subscription. If in doubt, check the full license here:
- For Items other than fonts and add-ons, a Single Use is the use of the Item to create an End Product (requiring an application of skill and effort)
The license starts when you Register your use of the item and the license is only valid if you complete the End Product while your subscription is active. Then the license continues for the life of the End Product (even if your subscription ends).