Going from a 32 to a 50T sprocket will decrease your top speed noticably but hills certainly won't be a problem. Unless you plan to be climbing very steep inclines you might want to explore something in the 40T range. That's an all round good gear ratio for most riding and riders.
If much of your riding will be on dirt then stick with the knobby tires but on hard surfaces, asphalt or concrete, a smoother tread will make the ride more comfortable. Any vibrations you have from the engine will seem to be amplified with knobby tires.
I like your attention to detail. That's always important when you want the bike to 'look' good.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"