Well... Even when you have say 150 platforms or sprites, Collision checking would be no problem. A simple optimization would be, to only collision-check the platforms that are on the screen.

But if you divide your game into alot of area's/levels, I don't think you need alot of optimization. And even if you need it, you can probably add that functionality later on.

I am planning on using Records and Record arrays for some manner of object data storage, bounding box data if necessary could be included in these object records also.
Why not using classes? :? You could use all the OOP tricks that aren't possible with records. e.g Make a base sprite class and derive the other sprites/platforms from that one. Good use of classes makes your life a whole lot easier.. I can tell you that.