@Threshold -
MacroDroid doesn't have that construct of guaranteeing to start a macro before any others; furthermore, it doesn't have the Tasker construct of priority either, which is how you can guarantee that a such macro not only starts, but also completes, before other macros.
To further
@Abalsam 's comment, MacroDroid's local, as well as global, variables persist after a macro finishes executing -- unlike in Tasker, That may help you avoid some of what you're doing in Tasker. (and it's a good feature in general -- helpful in debugging, etc.).
But if you do a macro to complete prior to all other macros, you'll need to implement something like the timer scheme suggested above. You would only need to write the logic once, in either a macro or a similar concept MacroDroid introduced recently called "Action Blocks". Then add a single step to the beginning of each of your (post-bootup) macros to call that macro/action block which would wait until your boot-up macro finishes.
I acknowledge it'd be nicer to have MacroDroid facilitate this more automatically, but I don't think there's a way to do that currently.