I think you are on the right lines. Nerdiness is more closely associated with academic and or arcane interests and geekiness is more closely associated with interest in tech, gaming, fantasy and sci-fi. There is overlap.
You could have a technophobic nerd but not a technophobic geek I think. The techie associations of geek are recent development, the words would have been more interchangeable in 1980.
When I was in the States in the 80s, geek and nerd were more interchangeable. Still, nerd was more what we'd call a swot, or clever, here, while geek was not necessarily technophile but social oddball. Pee Wee Heman in US, and Mr Bean here would have passed as geeks but not nerds.
Interestingly this American vernacular had not yet arrived in the UK. Usually it took about 5 to 10 years but has accelerated since advances in global communication.
Much more fun were other description of nerd/geek. The "jocks" would call nerdy geeky types "pencil necks." Always found that very funny. Most British men, about 5 foot 9 and 12 stone on average in the 1980s, would have qualified for the epithet.
Much more intriguing was the disgusted and dismissive "what a dweeb!" by the female of the species when describing an undesirable male. Usually nerds/geeks/pencil-necks all passed the dweeb test.
Strangely, Americans have never considered RVs geeky or old farty. Driving coast to coast in an RV is almost considerd an essential, as wholesome and American as baseball and apple pie.
So not at all old farts and geeks in their eyes. Just normal earthy people no matter what their background. I believe true in OZ as well.