It is one single westinghouse reactor of the same type that was used in Fukushima II. So essentially 60ies technology. I'm no nuclear expert but there surely is much improved more efficient and safer reactor technology now, not to speak of completely obsolete control and safety systems.
Also AFAIK it isn't really complete anymore as parts have been dismantled and sold to be used in reactors of similar vintage.
It is not a westinghouse reactor. Westinghouse doesnt and has never produced Boiling Water Reactors afaik. They mostly do Pressurized Water Reactors.
And while Fukushima and Zwentendorf had the same type of reactor (Boiling Water Reactor), it was not the same modell or from the same vendor. Fukushimas reactor was made by General Electrics. Zwentendorfs reactor was made by the German Kraftwerk Union.
Fukushima's BWRs were GE, Hitachi, and Toshiba. It doesn't matter who the official brand is on the side because they're integrated and supported on-site using consulting companies who probably designed them and probably worked for both or all 3 companies at some point.
I worked for the company of one the main guys who designed BWR-4, consulted on BWRs, came up with SBWR (never used) and ABWR, and submitted ALWR plans to EPRI that never really went anywhere because of public relations and regulatory climate. ALWR became the basis of some SMRs like NuScale. WH and GE Hitachi SMRs are BWRs.
You are right, its a GE design. Boiling Water Reactor doesn't say that much, the soviet RBMK (big reactor with tubes) also are of boiling water type. This ORF story https://noev1.orf.at/stories/504751 (in german) claims that the type in Zwentendorf is identical to those in Fukushima (I). Maybe it's not exactly the same type but the designs seem to be very close relatives.
Also AFAIK it isn't really complete anymore as parts have been dismantled and sold to be used in reactors of similar vintage.