of course it all depends on where you are located in the USA...
plan B looks best to me,
but you could live without the
vent to the kitchen with B, just put an auto air vent
as the shower shows it would already be vented..
maybe run 2 inch to the lavatory from the toilet
and then a 1 1/2 vent above
bigger is always better for the drain lines
let the debate begin