I think they are 40-406 tires, came with the OEM wheels.. those aero rims are really stiff in 20" size... or maybe because I run them at 45+ psi.
I don't really bother with tubeless & sealants, just plain tubes last me a long time... maybe when the OEM tires wear out I would try some wider tires just to give more supple ride on the mini frame.