Microhood vent location, diameter, duct type?
I'm not a professional builder, just a long-time DIYer. Until one comes along, here is my 2 cents opinion.
If it were me, I would use straight dryer type vent pipe because you will be exhausting cooktop air with grease fumes in it from time to time which may cling to the flex ridges and buildup over time, even though most of it is filtered out.
The vents of these units are usually out of the top. It can be 90ed to the rear from there (out an exterior wall from in the cabinet above), or taken straight up through the cabinets through the roof. A dedicated electrical receptacle will need to be in the cabinet base above the microwave/vent unit. A 15 amp circuit with 14/2-with-ground wiring is probably all that is required by your local code, but if you're running it new, I would run a 20 amp circuit with 12/2wg.
Do NOT try to share a bathroom and a kitchen vent. I had a homeowner DIY one like that once (I'm a Realtor), and he had to have it separated. There were kitchen odors blowing into the bathroom and bathroom odors blowing into the kitchen from that rig. LOL Keep the venting separate.
Also, make sure that the mounting bracket has at least one lag bolt in a stud behind the unit.