The train is reliable and civilised but costs money. You can use cash or a credit card in the ticket machines when they are working. But there's no smoking carriages any more.

Alternatively your fare may include a free transfer on the bus which serves the longterm car park. This can be a scrummage.

Don't recall a smoking lounge, all the space in the int. terminal is dedicated to a shopping mall and you are forced to take a detour in the opposite direction to the gates in order to lead you past the merchandise, ugh.

Perhaps best to smoke outside the building once you have your BP, before going thru security.

And OLCI if at all possible, check-in closes about 30 minutes ahead.

There's no rule about how early you have to be airside. [Not like LHR T5 security where there are BA goons whose job it is to tell you you've missed your flight and physically prevent you from getting on the plane if you're trying to get through within 35 minutes of scheduled departure.]

On the other hand there's sometimes a queue at SYD emigration control - slip into the fast lane if necessary.