"cover up the spacing of the floor to the landing with molding?"
I really don't understand this.
Is this a raised landing and you want to cover edges of flooring on it? Or gap between flooring below level of landing and vertical sides of landing?
Either way it would not be difficult to extend straight sides of landing to make right angle, and put joists inside triangle, if you want that sharp corner jutting out.
Depending on radius of curve. You can install flooring on landing over hanging curve, rout off flush with curve, cover edges with thin 1/4" slat of matching wood. Slightly releave upper out side corner with router or sand paper.
If covering gap, cut flooring to match curve, close fit 1/8", cover gap with 1/4"
slat applied to vertical side of landing. Releave upper outer edge.
There are also flexible rubber mouldings, base and shoe, that match wooden mouldings. Paintable and artificially grained and stained. May be local dealers or try google 'archetectectual mouldings; flexible molding.
You can build up thicker molding from thinner slats, applied individually and built up. Glue and nail each one. In shop with plenty of shapers, routers, gouges, planes, sanding, sweat and labor I have made such flexible laminated molding to match existing moldings.
A few pictures would certainly help.