I think Euge's video does a good job at showing the differences here.
I have experience with a few Engls. I've owned a couple of Fireball 100s, Fireball 25, and my other guitar player owns a Powerball 2. I spent a short time with a friends Savage. To my ears, Engl has 2 types of high gain tones, one based around the Fireball (Ironball, Powerball), and one based around the Savage (Artist Edition, Blackmore). Then the SE heads I don't really have experience with, but from videos it seems like they combine tones from both sides.
The Savage based amps to me seem more Marshally. More of that kind of mid range. Not that they sound like Marshalls lol. While the Fireball based amps have a more 5150-ish kinda of gain to them.
The Savage is RAZOR sharp. I would have liked to spend more time with it, but the time I did spend, it was lacking low end for me. Maybe how he had it dialed in, he doesn't like a lot of low end in his tone.
The Fireball is very open and aggressive and huge sounding. The Powerball takes that and compresses it a bit more, making it feel tighter. The Powerball 2 has been my favorite Engl I've played. And I've spent a lot of time with it. You can hear these differences in Euge's video.
The FB25 is cool, similar in some ways to the 100, but you aren't getting the same low end response. And it pushes more mids.
I've also played an Invader and Thunder, but I don't remember them too well, so can't really comment. I still regularly play the FB25 and PB2 that my other guitar player owns. They're both great amps.