You may want to consider going with a more DIY build vs the Ecoflow. I have one, and it's a good backup power solution, or for running a cooler fridge when camping, but it is not a UPS nor well suited to running daily loads (mine does not have LFP battery chemistry, so is only rated for something like 800 cycles).
I'd go check out what folks are doing for this sort of arrangement at https://diysolarforum.com - lots of good stuff there.
This advertisement for an awful commercial software package with a restrictive license in NO WAY helps the original poster learn FreeCAD.