No the floor must be OK to get water on (OSB is especially a no-no, though it's fine as a subfloor as long as you get OSB specifically rated as a subfloor [same applies to any room of the house]. Normally OSB subfloor is tongue-and-groove and usually around an inch thick.)
I'd suggest a ceramic tile for the bathroom (try to avoid smooth shiny tiles since you're more apt to slip and mutilate yourself on either the tub, toilet, or sink, all of which would hurt like heck lol). If you choose a laminate floor for the bathroom make sure you use a water and mold resistant subfloor. God forbid the toilet, tub, or sink overflows. OSB will swell up and buckle and make the floor look horrible. Not to mention after a couple times, the OSB might be structurally sound, as the water will likely sit in spots you can't reach to mop up and soak into the glue and undo it.
I just don't even like to think about bathrooms lol. WAAAY too many codes and special requirements. Electrical is actually the least of the code headaches. The only requirement I'm aware of is that one GFCI outlet is required along the countertop of the sink and this outlet must be supplied by a 20A circuit dedicated to bathrooms. (If you have multiple bathrooms, they can share the same 20A circuit as long as the circuit only powered bathroom receptacles. Lighting must be on a separate circuit; 15A is acceptable as long as load calculations do not contradict. i.e., if you have six bathrooms with exhaust fans with heating elements, you would probably want to break that up)
If each bathroom has its own 20A circuit, lighting can be included on the circuit with the receptacle. Under no circumstances can the 20A bathroom circuit supply anything outside of the bathroom.
Here's a good article. This Mike Holt guy has a lot of informative articles that I refer to when I have questions. In addition, for receptacle placement, the receptacle must be installed somewhere along the sink's countertop. In my bathroom, the sink countertop is against the corner of the bathroom by the door. The GFCI is in a 2-gang box with a light switch for the vanity and is installed on the same wall as the door. There is another 2-gang box next to the door, the switch closer to the door is for the light and the switch further from the door is for the fan. When wiring multiple switches like that, the switch closest to the door should be for the light. When all the switches control lights, the switch closest to the door should control the light or lights closest to the door. I don't know if there's a specific code that requires this, but it's been a common thing with any place I've ever been. My house, all the school classrooms I've been to, other people's houses, etc.
Once that single outlet by the sink has been installed, additional receptacles can be installed (near the toilet for instance, like if you want to plug in your phone while you're taking the browns to the superbowl) though it's not common. It opens up another can of worms too, since there are regulations as to where those receptacles can be places in relation to the bathtub (basically they want the outlets further from the bathtub than the length of the cord on a hairdryer lol).
If you plan to install two sinks in the bathroom (I think it's a waste of space but some people like two sinks in their bathrooms) install the required receptacle between the sinks, as the outlet must be within 3 ft of any basin in the bathroom ("basin" being sink).
For bathroom lighting, if you use track lighting or pendant (chain, downrod, cord, etc.) lighting, those lights cannot be in the "shower zone", which covers a 3ft radius around all sides of the tub or shower. Recessed or surface mount lighting CAN be installed within the shower zone. Lights installed on the ceiling within the "shower zone" must be marked for damp locations and lights subject to spray from water must be suitable for wet locations. I personally like having a light over the shower so I'd install a recessed can over the shower with a shower trim on it, which has a lens of some sort (drop dish opal or Fresnel for example).
I think that's pretty much it on electrical code for the bathroom. So basically to sum it all up short-n-sweet, you need a 20A circuit exclusively for the bathroom. You need one 20A GFCI mounted within 3ft of the sink. Except for recessed and surface mount fixtures, no part of fixtures can be installed within 3ft of the outer perimeter of the shower/tub. NEC also goes far enough to say the edge of ceiling fan blades cannot be within three feet of the shower zone either, but I've never seen a bathroom with a ceiling fan lol. When recessed or surface fixtures are installed within the "shower zone" they must be rated for damp locations.
If you want, I can email you pictures of my bathroom and my parents bathroom. The set-up is essentially the same in both as far as the electrical is concerned.