You can use the term システムバス (system bath) to search google for Japanese style bathrooms and ウォシュレット (washlet, toto trademark) or 温水洗浄便座 (generic name for heated toilet) for the heated/bidet style toilets
Basically, it sounds like you are looking fro Tim Allen’s “Man’s Bathroom” from Home Improvement. Home Improvement clip of 'The Man's Bathroom' segment - YouTube
I am not a plumber, but in a shower cubicle you basically already have a raised floor - either the bathtub or there is a “tray” or concrete under the tile. It’s not always obvious because the floor height difference is somewhat hidden by the lip you have to step over in most setups. To install a floor drain you basically have to do that for the whole floor - slope it towards the drain + either raise the floor up enough to fit the drain piping & trap between the joists (since the drain is going to be at the lowest point of the floor), or have it stick out into the basement some (easiest).
Toto Washlets are certainly available with English-language controls and instructions; we have two of them. They are not super-expensive, depending on which model and features you get.
Japanese homes generally have a separate room for the toilet, that is not in the “wet room” area. The wet room usually has a shower area, a soaking tub, and the on-demand hot water. No cabinets, and the only wood might be the tub cover (to keep the water warm so that it can be re-used for laundry). That will be the inner room of a 2-room area; the outer room will have the sink, vanity and mirror, and probably places to hang up wet towels or to hang your clothes while you bathe. Sometimes this area will also contain a washer & dryer.
The WC will be a 3rd separate room, probably next door to minimize plumbing runs, about the size of a small closet. No sink or vanity in there, but often the water refilling the tank will come out in a small faucet above the tank so you can rinse your hands in it. Of course, if you are using a washlet you don’t really touch anything so washing is less important.
I don’t think having a wet room is a particular problem for building codes; it requires a floor drain, as well as the tub drain, which is extra construction; other than that, everything can be pretty normal. You probably need a curb between the wet room and the outer room to keep all the water inside.
I kind of wanted this arrangement, except that I was going to put the toilet in the outer room instead of a separate WC, but I didn’t have enough room. Good luck!
Roddy