It is very easy to adapt a 1.8 engine into a 1.6 using the 1.6 electronics. All you have to do is adapt the 1.6 sensors into the 1.8 engine JUST make sure you keep your existing alternator the one in your car now, otherwise you will fry the ECU.
Flying Miata sells a kit to adapt the 1.6 coil packs in the 1.8 block and some other components to block the EGR sensors; with regard to the Throttle Body *you have a 1.8 NB so it should be a direct fit* if not you can purchase an spacer (check Flyin' Miata) or simply remove the intake manifold, take it to a machine shop and ask them to weld the lower threaded holes and tap with new ones to adapt the 1.6 TB.
Also the 1.8 BP engines are fitted VVT, VICS, cam angle sensors and crank angle sensors. You don't need to pay attention to those unless you want to upgrade the ECU or they are components of your factory harness. The only other issue I foresee is to how retrofit your existing OEM cam angle sensor in the 1.8 engine. The corresponding connector wires related to the cam angle sensor may be too short due to the fact 1.8 the cam angle sensor location is on the driver's side of the valve cover. You have two choices cut and extend the harness or do it the Baller way, do a wire tuck and see if you can extend the wires without cutting them.
Good luck
EDIT: Below find pics of my old 1.8 Protege Turbo engine with 1.6 electronics
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