Sounds like a Repack replica throwback to the 60s to me..
Smoking the grease out of coaster brakes on downhills required re packing.

MTB tires are for Dirt fire roads roads , Loose gravel , not pavement,

but for the mountain bike market segment there are road tread tires ..
still not super easy rolling high pressure but you can get closer.

Schwalbe big apples are wide comfy but easy rolling, I'm told,

I'm running their Marathon Plus tires , adds a very puncture resistant tread design.
559-47

559 is the international standard bead seat diameter measurement rims and tire makers agreed upon.. for the mountain bike 26"

you should get a tire a little wider than your rim, as a minimum... 47 is like 1.75"