As also other big cities at the time, like Lutetia?
At its peak, Rome had 1 million inhabitants.
Did people had individual toilets and septic tanks at home?
I know that most, if not all, Roman citizens didn't have bathrooms and kitchen at home. So they relied at public bath and tavern/restaurants.
Were there public toilets too? Were poo floating in the city sewers?
How did garbage disposal work?
Rome had public toilets, a subterranean sewer and public baths, but by all accounts the city was filthy. Stepping stones were places in the street so that people could cross the street without stepping into the filth covering it. People often dumped waste into the streets, rather than use the public toilets, so it would have been disgusting by our standards. Rome was certainly not a clean city, but relative to other cities of its time, it was significantly more advanced with public sanitation.