I'll try to answer your questions in the same formatting for clarity:
Yes, you can use marketplace themes, drag and drop, as well as custom themes from the design manager
I don't think so, but not 100% on this. You should reference the internal ID associated with the email. I commonly use a Gsheet to keep track of these.
Yes, you can use pre-defined templates using the Single-send API. The Single-send API sends template emails created in the HubSpot email tool using a JSON-formatted POST call.
Yes, you can use the SMTP API and the Single-send API.
Yes, you can A/B test transactional email content to optimize your overall transactional email performance.
Note that you need the transactional email add-on to use these APIs.
You can refer to this article to better understand how to use the Single-send API.
Yes, you can use pre-defined templates using the Single-send API. The Single-send API sends template emails created in the HubSpot email tool using a JSON-formatted POST call.
Yes, you can use the SMTP API and the Single-send API.
Yes, you can A/B test transactional email content to optimize your overall transactional email performance.
Note that you need the transactional email add-on to use these APIs.
You can refer to this article to better understand how to use the Single-send API.
I'll try to answer your questions in the same formatting for clarity:
Yes, you can use marketplace themes, drag and drop, as well as custom themes from the design manager
I don't think so, but not 100% on this. You should reference the internal ID associated with the email. I commonly use a Gsheet to keep track of these.