In the case of an overflow, there is not much you can do to protect the floor.

If you had a tile floor, the overflow would find its way under the vanities and baseboards. So those would have to be dried out and maybe replaced. If you have a wood floor, you just add the floor to the equation.

Depending on how long the overflow is there (and what kind of overflow it is), you may have to replace the wood floor too.

In a powder room, it's not a great risk. In a family bath, I wouldn't add wood floors. However, I purchased a home that had wood floors in both bathrooms. There wasn't really any damage to the wood floors when it came time to remodel those baths. But I didn't keep the wood flooring!

You can't. if you are concerned about that - the answer is to not do wood.

Don't do wood floors in a bathroom. It isn't just the overflow. It's the overspray and everything else.

Overflow is overflow- it can mess up any floor depending on how much over the flow was. But some splashy from normal use is different. There has been wood floors in bathrooms before tile, and still is done. Lots of bathrooms have lots of other wood in them and it works fine. Kitchens, laundry, and mudrooms have wood floors too, and they hold up depending on treatment and use.

It's not the wisest or most popular bathroom flooring option. But it can be done. Seal the beejeebers out of it. Be prepared to keep an eye on it to keep it clean and dry, maybe a bit more so than a non-wood floor if it might see a lot of splashy use. If you have kids, maybe hold off on the wood or train them to use it well. Perhaps consider wood look options.

Have you considered wood look porcelain tile? many nice looking options available