Both! I started it without permits because I had a general idea on what we wanted to do but I didn't really have a full on plan.

The engineering stuff is a pain, but what I did was I basically over engineered the hell out of it. Once I did that, it was really cheap to get an engineer to sign off on it.

Once you are past that, the rest is just do as you go. You will probably get a few things wrong along the way, we did when it came to electrical code for sure, but if you have good inspectors they aren't mean or discouraging. The inspector here was actually extremely nice and easy to work with. He did a good job explaining things and didn't make you feel like a dumb ass