In reverse order:
The rail used on AtlasO 2 rail track made since the 1990's is code 148. This product line is made in China and has brown plastic ties. Back in the 1970-80's Atlas imported 2 rail O scale track made in Austria by Roco. The rail was nominally code 152 and can be spotted by the black plastic ties. Heads up - early production Atlas-Roco track used nickel plated brass rail and under heavy use (or cleaning) the plating will wear off leaving a brass rail top. Late production Atlas-Roco and all Atlas-China track featured solid nickel silver rail.
Atlas 2 rail turnouts have frog and guard rail flangeways formed to NMRA standards which do not provide clearance for the deep and thick MTH 3 rail wheel profiles. If you are going to go 2 rail my recommendation is to lay your track to NMRA standards for brand independent smooth operation.
