With Arncliffe being so close to the airport, is it noisy during the day, night or weekends?

Absolutely not. The flight paths are actually either side of Arncliffe - basically over Rockdale and Sydenham. I've lived in 2 streets (Atkinson and Stanley) and you hear nothing.

Arncliffe is between the north-south and east-west runways, there is no noise and no planes flying overhead unless you happen to live in the south-south-eastern corner of Arncliffe, in which case you may be under the east-west runway (which only carries ~4% of the overall airport traffic). We had quite a lot of aircraft noise in our previous suburb Marrickville, but now we're closer to the airport and we can see the airport and the planes from our loungeroom, but we never hear them.

You will hear noises, but most of the time the birds in my garden is alot louder than plane noises.
If you are comparing to Inner-west suburbs(Burwood, Marrickville etc) Arncliffe is consider very quite.
There is the odd one that fly over us, but being so close to the CBD we are very lucky as it is.