This is what I would consider hi-tech, and low tech;
Hi-Tech: Good Lighting 2.5wpg or more, Pressurized CO2, doses ferts, monitors/controllers, automation...
Low-Tech: Low Lighting 2.5wpg or less, DIY CO2 or no co2, ferts or may not dose, no monitors/controllers, no automation
A low tech tank may have good lighting say 3wpg, and may dose ferts, and diy co2, but no automation no controllers, I would consider this a low tech tank. To be high tech I think a tank would have to have all the requirements of the hi tech that I listed above. Anything less would be low-tech or even mid-tech...