You mention swivel, not sure if you mean bounce (head points up to bounce light off the ceiling) or rotation (head turns to the side, which would let you bounce off the wall or if in portrait mode off the ceiling).
The 90EX has a fixed head. No rotation or bounce capability, no head zoom (fixed at 24mm coverage). Pretty sure it’s discontinued, may be available, likely used. The key feature provided by the 90EX is that it’s an optical master. It was bundled with early M-series bodies (the M and M2 had no popup flash).
The 270EX II has bounce (manual to 60°, 75° or 90°) and zoom (28 mm, manual pull out to 50mm). No rotation. I have this one, it is my travel flash for the M kit and I’ll be bringing it on my upcoming trip with the R8. Pretty sure it’s also discontinued, may be available, likely used.
The EL-100 is current, Canon’s entry level flash. It has bounce (up to 90°), rotation (up to 180°) and zoom (24mm and 50mm). If I had to buy a new travel flash today, I’d get this one.
Compared to the EL-100, the 270EX II is smaller (about 2.5 cm / 1” shorter), and lighter. Power is basically the same, but the 270 supports HSS, the EL-100 doesn’t.