Slightly off topic, but if you are looking for a good product to disinfect your shower and clean mould, I would seriously consider Hydrogen Peroxide.
The H202 structure of Hydrogen Peroxide means that its just an unstable form of water with one extra oxygen molecule. When, oxidisation occurs, one extra oxygen is released, so, all you smell will be oxygen.
Its also way cheaper to NaOH, non toxic and can be used almost anywhere.
Sodium hydroxide is a strong alkaline, and reacts to acids and is effective to break down oils, and scale, But beware, it will burn your hands, its a good idea to wear gloves and if you get some on your hands, was with vinegar water solution.
the NaOH will clean the grout really well, but it will weaken and you will get soft grout essentially many grout cleaners use NaOH as an ingredient. I think for a once off clean (provided you work in a really well ventilated area, and use all the protection, you could use it as an initial clean) thereafter i would switch to H2O2