Mikaele-Tu’u, 23, will join up with Rhys Jones’ side on Monday, so is not available for Friday’s Premiership Women’s Rugby opener against Loughborough Lightning.
Sae, 25, is due to arrive at the club from Hurricanes Poua on 10 November, before Quins’ visit to Exeter Chiefs.
Sae has 19 international caps while Mikaele-Tu’u has 35 and was part of the Black Ferns’ World Cup-winning squad in 2021.