Both the photos you have posted have concealed pipes behind the tiled wall. So no real difference, only aesthetics.

If you are worried about the pipes leaking, then get them installed like this. These are exposed pipes with no connections through a tiled wall.

Thanks! you are a hundred percent right—im going to buy a shower set, including a handheld shower and a overhead (rain) shower. and could you give me more suggestions about this.

1.If it’s a concealed (in-wall) setup, how many water outlets is usually ideal, or how many holes do we need to cut in the wall during the rough-in ?

2. Should the handheld and overhead shower share the same outlet, or is it better to have separate outlets for each?

3.Also, is this something I can install myself after buying the set, or would it be better to get a professional plumber to do it?

All plumbing should be done by a licensed, qualified plumber.

If you look at the photos you have posted, the amount of inlets/holes required can be worked out. It differs depending on the fixtures used.

To be honest, I have absolutely no idea how many inlets/holes i need to prepare. This is my very first time managing a bathroom renovation by myself, and I'm a complete novice.

My old bathroom only had a single, fixed overhead shower, and it was a total nightmare—you could hardly stretch the water to clean the tiles. My friends are all rookies too, so they couldn't give me much useful advice.

you' ve mentioned that over 90% of Aus homes use concealed plumbing and now I need some pro tips on the layout: Which setup is more practical for daily use? Should the handheld and overhead shower share a single integrated outlet/mixer unit (2 holes in total), or is it better to plumb them as completely separate outlets (3 holes), thank you for your kindness and useful suggestion.

You need licenced plumber to rough in and then return to fit off. This will come with warranty and is the law