Stud wall centres. Residential vs Commercial

[ApeWrangler]

Sorry if in wrong forum but its for a bathroom so....
I'm building a stud wall in a large garage to section off a new bathroom and office space. My sister in law is designing the renovation and she is a very experienced retail architect having worked extensively in Europe and Australia. She is insisting that we can build the stud wall (not load bearing) with studs on 900mm centres (she says 918mm is her exact number she uses regularly). Australian 'code' for residential says 450 or 600 centres. We are not required to get a planning or building permit for this. Wall will be just under 2600mm high. She also says we can achieve good insulation qualities using 75x30 studs and that we don't need 90x35 which I was leaning towards. Garage will see minimum temps of about 1-2 deg C on the absolute coldest of winter nights.

Anyone have any thoughts on these dimensions? We will be doing all the work ourselves.

[mic-d]

Code say max 600mm between centres. And I’d presume thicker walls allow better insulation. Why try and penny pinch on what will be a small extra cost. I’d probably use 90x35 at 450 centres for a bathroom to allow for any heavy cladding like tiles you or a future owner might install. Go 90x45 if you’d like the leeway it offers you putting sheet joints over studs or just making it easier to hit studs with fixings.

[droog]

What wall sheeting is to be used and what does the installation guide for that sheeting advise ?