1 and 2 are both below the Minimum Recommended Hardware for Tableau Server, neither would be recommended for a production instance:
Free Disk Space
8-core, 2.0 GHz or higher
Capacity planning for Tableau Server is based on more than concurrent users, you'd also need to take into account the data sources and types of data that will be used, the complexity of workbooks and how often that are accessed for interaction/authoring, the frequency of data extract refreshes and the size/complexity of the extracts being refreshed. There is a Services offering specifically geared to help plan your Server environment. If you have a Sales Account Manager, they can put you in touch with resources on this front.