Both should be possible, as long as days are relative of course (i.e. x days from or before today), absolute dates don’t make sense, then you can just as well hardcode them in the template. So with this in mind it should be possible since we added support already for that:
the same is true for reminders, you should already be able to just type in the remind shortcut in this way:
As long as you keep in mind that dates and reminders are always relative to the day on which you create a note from the template, you can work relative from there.
So for instance, you can if you wanted to create a “Sunday night template” that creates a note with reminders for things on Monday etc. However, if you go this route, I would suggest to invest a bit more time in the shortcuts route, this allows you a lot more flexibility and could literally spit out an entire project for the week independent whether you trigger it on Sunday eve or Monday morning, etc etc. You can even combine the two, have basic templates that you use within an (automated?) shortcut etc.