Ross has an O42X make up piece for the O42 switch to take it to 45° and O42P to bring it to parallel.
You'll have to cut for the O54.
read about Gargraves track specifications on their website. The diameter is "nominal" - not center rail like Ross. A Gargraves is a 54" diameter to the outside rail and the Ross is a 54" diameter on the center rail.
This is where software will help with the fitment for a build plan.
If you are going to use sectional track, I would suggest that you use all Ross.