I've seen a viral post about a toddler who passed away after getting stuck between their bed and the wall. The recommendation on the post is to have the bed at least 30cm from the wall. Is this what red nose recommend as well? If it's a small bedroom, is it OK to have the bed against the wall but with a bed rail on both sides? Just want to ensure we're following best guidelines when we move our son from his cot.

Red Nose does not recommend a specific space between mattress & wall.
As far as bed rails are concerned, it is important to ensure there is no risk of entrapment either.
Red Nose has the following information in relation to cot to bed safety:

FLOOR MATTRESS One option is to take the mattress from a cot or a full height single bed and use it made up on the floor. Ensure the mattress is positioned away from the walls as young children can become trapped bet ween the mattress and wall. A child’s mattress needs to be firm to prevent sleep accidents. Keep the area around the mattress clear of soft toys, bean bags, plastic bags or similar objects that a young child can roll onto. Soft objects could mould around a young child’s face, resulting in suffocation.

PORTABLE BED RAILS: If you have decided to attach portable bed rails to an adult height bed to prevent your child from falling, be mindful that children can become trapped if the rails are not fitted properly. Before placing your child to bed check that the portable bed rails fit tightly against the side of the mattress and there are no gaps bet ween the mattress and the bed rail. This will help prevent a child’s body or head slipping through and becoming trapped

A child no longer sleeping in a cot has greater access to all living areas. Before your child graduates to a bed, check your child’s room and throughout the house for possible hazards.

Other information about cot to Bed safety can be accessed here:
https://rednose.org.au/article/search/eyJyZXN1bHRfcGFnZSI6ImFydGljbGVcL3NlYXJjaCIsImtleXdvcmRzIjoiY290IHRvIGJlZCJ9