Ok, I think I understand. The video you are watching is from SFS 1.35, which is an older version (current version is 1.4.06).
The parts are not the same indeed, but parts available in 1.4 allows normally to do everything that was possible under 1.35 and more.
For example, you don't have the conic section anymore, but 1.4 introduced procedural parts, which allows parts to adapt in size:
In the end, version 1.4 provides you much more choice. For example you didn't have access to fuel tanks wider than 6 blocks under 1.35.
The only real loss is the big probe, but there is a way to get it by manually editing the blueprint. But you may prefer discovering the game you've just purchased before getting into such things