I had a so called ‘mild case’ as well, so much so that my GP thought I had a pinched nerve when I told him i had pins and needles in my arms and legs. In the beginning the only reason I was taken seriously at all was because I had an elevated CK level in my blood test.
And so after having CT scans to rule out cancer, I was referred to a neurologist to investigate things such as ALS. Finally came out with the GBS diagnosis.
My EMG/NCS was clean too, and all I can tell you having been forewarned that they were looking for evidence of motor neurone damage, is that a clean EMG is an excellent outcome. Be happy that your EMG was clean, and whether GBS or post viral syndrome the treatment options seem pretty much the same (i.e. time, time and more time).
My neurologist told me that in people with ALS, the EMG is never clean if symptoms are present, as the disease starts before the symptoms are apparent (makes sense right?) So if you had a clean EMG, its not possible that it was too early, or something was missed etc so please don’t worry about this.
And even with a clean EMG I was still diagnosed with GBS. (I had a normal MRI too).
The main thing is you say you’re improving - this is the best sign!
Good luck and keep getting better