The #1 thing to know is that the model numbers indicate the tiers from low end to high end. Just like the tiers of Fenders, there are so many tiers it can be mind boggling.
The Mikro range is super short scale (28.6") and low end.
The Mezzo range is 32" scale, also low end.
The RGB range is aimed at metal, complete with pointy headstock. Current models are low end, but there are older higher end modles out there.
The EHB range is the fanned fret models.
The Talman range is "Fender inspired".
The old ATK range is "Stingray inspired".
SR is the main range, the high end models are pretty amazing in build and sound. Low end gives you the classic fast necks but with a low end sound. Current tiers are 100, 200, 300, 400, 500, 600, 700 then into four digits for the high end stuff. 100-300 are the "beginner" range. For years, the 800 range was the standard model but no longer made.
The BTB range seems to be an alternative to SR aimed at buyers who want boutique (Fodera, etc.) style at a lower price. The high end models are stunning. There are more 6 string options here than in any of the other ranges, but no 4s at all.
Workshop = custom shop
Prestige = MIJ
Premium = high end Indonesia
Only the real low-end models like SR100, Mikro, Mezzo are passive...maybe Talman as well?
The active electronics vary widely from the bass boost "Phat EQ" in the 200 and 300 series to sophisticated multiband EQ stuff. As you get into the high end you start seeing Bartolini designed pickups and preamps. Some of the early models in the SR1000 series back in the 80s came with EMG pickups and are worth looking for used.