Plummer was initially assisting the South Africans but took over as head coach last month after Netball South Africa got the green light from the international body.
"They are a team on the rise so it'll be great for us to get that level of competition," said Taumaunu.
"They've always been very tough and competitive, and that will remain the same. But Norma has always been renowned for teams that have great timing, and very good core skills, so I expect we will see that too."
Taumaunu also expects Fiji will be much stronger from the last time they met, the Pearls having had a lot more preparation time together.
"I think they'll be a bit fitter now and a bit more experienced, so they will offer a slightly more compelling contest and play a style that will mimic a couple of teams we're likely to face in Australia."
The Ferns' chief concern in their upcoming games will be getting their new attacking combinations firing, with just over two weeks remaining before their opening World Cup clash against Barbados.
Rookie shooter Malia Paseka will probably make her first test appearance tomorrow night, and the Ferns coaching staff will be hoping she quickly finds her feet in the New Zealand attacking unit.
Tomorrow will also probably mark captain Casey Kopua's return to the international stage just over nine months since she was carried from the court with a serious knee injury in the Ferns' third Constellation Cup test against Australia.
Taumaunu said the next three tests would be crucial to Kopua's quest to return to top form before next month's tournament.
"The knee is 100 per cent, she's still working to get her netball form back, but hopefully this series will provide her with the opportunity to regain that confidence and timing," the New Zealand coach said.
Taini Jamison series
Tomorrow
Silver Ferns v Fiji
7.30pm, Te Rauparaha Arena, Porirua
Sunday
Silver Ferns v South Africa
7.30pm, Claudelands Arena, Hamilton
Tuesday
Silver Ferns v South Africa
7.30pm, Trusts Stadium, Auckland
Silver Ferns team
Casey Kopua (c), Laura Langman (vc), Jodi Brown, Kayla Cullen, Leana de Bruin, Shannon Francois, Katrina Grant, Phoenix Karaka, Bailey Mes, Malia Paseka, Grace Rasmussen, Maria Tutaia.