Extended Licence Query - Individual Use or Enterprise For LTD Company?

Credit packs are well suited for what you intend to do. Indeed, Individual, Teams or Enterprise are Adobe terms to specify different models of subscriptions and not the type of your incorporation. Even a thousand employee company could buy licences based on an individual account via credit packs. Managing the different licences is just not possible with an individual account, as nobody else than the account holder has access to the licensing information. With a Teams or Enterprise account, those information are shared with the users and administrators of that account. From the Adobe stock point of view, that is the major difference, appart from a centralized innvoicing.

For Creative Cloud subscriptions, a Teams/Enterprise subscription does allow for more control about licence attribution and program installation/distribution and asset attribution. 

In your case, even if you would hire a permanent or temporary helper, the helper could use the asset to prepare the data into whatever you decide about. Licences are attributed to customers. This means that for each client you will need a new licence. Internal or external own use is consuming a licence too. As for all the rest, the licence is perpetual. 

This said, the licensing terms are quite straight forward. For using an asset on T-shirts you will need an extended licence. It's even named as an example application for illustrating merchandizing applications, if I remember correctly. 

Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788
(Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based on reading and interpreting the licence terms and on fair use for both the buyer and the artist/stock company, but I cannot rule out that my interpretation is wrong. I'm not an Adobe employee).