The only option right now to give you more detailed control over emails (and also allows HTML emails) is the relatively new extension Automated And Conditional Emails:
https://stephensherrardplugins.com/plugins/volunteer-sign-up-sheets-automated-and-conditional-emails/
This is a very complex extension that I did as a subsidized project for one specific client, and it’s a bit hard to understand what it does, how to set it up, and what you can do with it, so there have only been a few purchases so far. However, one of the things I have done since its release is to set it up so that you can pretty much replace all the regular emails with this system using various triggers. You would then just disable all the emails in the main/free plugin that you want to replace with this extension.
This extension gives you much more control over the emails as you can set email triggers for only specific sheets (as opposed to globally), and you can set up various lists for who those emails will be sent to (which can be specific emails, or can be a generated list of people signed up for that sheet or task, etc).
It’s very flexible and powerful, but you need to have a bit of a technical mind to set it up correctly. Don’t need to be a programmer, but a basic understanding of logic helps. Otherwise, you are correct that the settings in the main/free plugin are global and can’t be set for individual sheets.