I'll put here few numbers regarding wheels and you can decide or correct what is heavy what is light.
Bicycle wheel:
Tipical 26'' ready to ride front bicycle narrow wheel less 2kg (narrow alum rim, narrow 2'' tyre)
Little bit more beefy ready to ride front bicycle wheel 26'' up to 3kg (the same narrow rim, but wider tyre), maybe even 3.5kg with fat rim and offroad tyre.
rim from 400g (regular) to 1,3kg (fat bike)
tyre from 500g (narrow) to 1,5kg (offroad 3'')
MC wheel
17'' x 1.4'' alum rim can be 1kg,
17'' x 1.6 alum rim about 1.3kg,
Narrow skinny 2 ply tyre of width 2'' - 2.75'' ranges from 1.8kg to 3kg,
13G / 2.6mm spokes about 400g,
tube - 500g.
If you use light mc components for your rear wheel than you might get few kg over than using very light bicycle components for rear wheel and be equal by using heavy fat bicycle parts.
If you go mc rear rim than main rule is go with alum rim and light tire. Moped tyre is basically less material by having less plys softer sides for speeds up to 80km/h or 100km/h. Less than 2 kg is very light moped tyre usually for light skinny moped.
But if you really want to save weight than carbon instead steel/alum.