Not sure exactly what you mean by "range extender style".
By strict definition, that would be a vehicle with no mechanical between the ICE and the drivetrain. That eliminates all but the BMW i3 REx.
Both the Clarity PHEV and the Volt will function as either serial or parallel hybrids. In serial hybrids, the ICE functions as a generator for the electric motor(s). Parallel hybrids link the ICE directly to the drive wheels. The Volt stays in Serial mode more than the Clarity.
From Honda's press release:
The Clarity Plug-In operates in three different driving modes, depending on the driving situation, and is able to shift instantly, automatically and seamlessly from one mode to another to optimize overall efficiency:
In EV Drive mode, the Clarity operates like an all-electric vehicle – the engine is off and is decoupled from the drivetrain to reduce friction. Motive power comes from the 181-horsepower traction motor, which draws electricity from the lithium-ion battery pack.
In Hybrid Drive mode, the Clarity functions as a series hybrid. Like EV Drive mode, motive power comes from the electric traction motor. The coupled gasoline engine and generator motor produce electricity, which is sent directly to the traction motor or to the battery pack, depending on the driving situation and the battery's state of charge.
In Engine Drive mode, which is typically engaged when cruising at medium to high speeds, the Clarity functions as a parallel hybrid. A lock-up clutch connects the engine (always linked to the generator motor) and the traction motor to send power directly from the engine to the front wheels. Unlike most competing hybrid and plug-in hybrid vehicles, the Clarity does not use a conventional transmission, which saves weight and minimizes complexity while improving efficiency.
As to PHEV's available, we (the Oregon Electric Vehicle Association or OEVA) have a series of comparison sheets that show pretty much what is available on the market.
The sheets with only an orange circle under range are 100% electric (BEV's), those that also have the green oval are PHEV's.
I've driven all but a few of the vehicles on those sheets, so can provide at least a little feedback.
5 seat belts is, in reality, a stretch for the Volt. The middle seat in the back is barely suitable for a child. The Clarity is far roomier than the Volt in the back seat. The A3 is nice, but the electric range is relatively short - but it is a hoot to drive and the build/Interior quality is up to Audi standards.
Others that can seat 5:
Kia Optima PHEV
Hyundai Sonata PHEV
Chrysler Pacifica Hybrid
BMW iPerformance models (3, 5 and 7 series plus the X5) - relatively small Electric range
Cadillac CT6 Plug-in
Kia Niro PHEV
Mini Cooper S E Countryman All4 Plug-in Hybrid (I think the name is longer than the car)
Mitsubishi Outlander PHEV
Hyundai Ioniq PHEV
Mercedes C350e and GLE 550e have token Electric ranges
Porsche Panamera and Cayenne E-Hybrids
Volvo XC60, XC90 and S90 T8's
Not sure how important various factors such as electric range, price, body style, "luxury" factor, etc are to you, but there are lots of choices with more coming all the time.