Driving in Italy is THE best way to see the countryside. You'll see beautiful little towns that you would never possibly stumble upon if you only caught the train everywhere; especially in Cinque Terre and Tuscany. Too many times we've accidentally stumbled into a little town, with no foreign tourists and wished we could stay there for days, it's literally god's country.
Rome... Can you drive in Sydney ok? If so, you can drive in Rome; it's really no worse.
Download offline maps in Google Maps app on your phone, or if you're not worried about data use (if you haven't bought heaps of roaming data, or a local SIM), use Waze. Those apps are both constantly updated with current roads, will tell you which lane to be in, fastest route etc. Much better than factory-GPS systems in cars. Our latest trip to Italy (Oct 2019) we had a Fiat 500X which had Android Auto, worked a treat.
Highways are outstanding; ignore the speed limit signs because they're meaningless - you'll be on a 3-lane each way highway, sign will say it's a 60 zone or something stupid like that, while everyone is doing 120+, including the Carabinieri (police)! Good luck guessing what the "appropriate" speed to drive is though - best tip for that is just to stick to around the same speed as most other drivers. If a few cars overtake the Carabinieri, it's ok for you to do so too!
Country roads are easy. Except in some places, like Amalfi, they can get VERY skinny. So skinny that I've seen buses [driven by local bus drivers] get each other stuck, squeezed between two cliffs or buildings. My partner completely side-swiped our Fiat against a cliff wall, misjudging how much space she had. On that note [and I almost can't believe nobody in AFF forum picked up on this!] - check out whether your credit card(s) insurance policies will cover hire car excess. I have an Amex Qantas Ultimate, which includes (well, did back then anyway, haven't checked since Fortress Australia's walls went up) hire car excess cover - so I didn't pay the [ludicrously excessive!] "zero excess" fees from the hire company (either Avis or Europcar, can't recall which I used)... I just paid their large excess on my Amex (maybe 1500 euro or something like that?), which was pretty quickly refunded by Amex.
The other tip on hire cars in Italy, is that you do NOT want an upgrade!! Get as small a car as you can possibly live with... When we went to Amalfi we ordered a normal Fiat 500 (as in the baby 2 door) and I was so annoyed that we got upgraded to a 500X - which of course ended up in damage because it was too big for the roads (for my partner's driving skills anyway!). But Cinque Terre and Tuscany are better, we've driven a VW Golf around there without any problems at all. Tip for parking is just to stay away from major tourist areas and the middle of cities... I guess the caveat to that is if you can walk (when going to the bigger cities). Having said that, we managed to score a parking spot in a paid parking station in the middle of Florence (not cheap, but it was only for a few hours).
Happy travels and good luck!