HOW TO: Non-Lucrative Visa entry + freelance work? (Granada)

Hi everyone, and thank you for your help! Has anyone here entered Spain with a non-lucrative visa (and followed up with registration to formalize the corresponding residency once in Spain) and then changed (during the renewal period) to a work-permitting residency? (I hope to do this by way of the modificación for cuenta ajena, the modificación for cuenta propia, or the modificación for trabajo por profesionales/investidores altamente cualificados). If you’ve been down this road before, I’d really appreciate hearing about your experience. I know I’ve got a lot of “figuring things out” ahead! Thank you very much!

On a related note: I do freelance work (for clients outside of Spain). I’d originally understood that I could continue doing this work and simply “choose” my tax home to be the USA. That was wrong: I understand now that, if I’m doing the work from my internet connection in Spain (and for more than Protected content of year), then I’m working IN Spain and my tax home necessarily becomes Spain. Obviously I want to comply with my tax obligations and declare my income taxes to the Hacienda. Does anyone know if I can do that, and if so, what sorts of special declaration I might have to make since I will have entered with the non-lucrative visa? (If you can point me to the go-to government references, all the better.)

Thank you very much! (You can tell I’m a newbie!)