CVS was a nightmare because it let you nest branches ad-nauseum: it simply created a new dot with a new numeral below where you were, e.g. if you branched 18.104.22.168 it became 22.214.171.124.x
SVN lets you create your own branch hierachy, just don’t count on anything to really understand it.
For many projects branches are significant ancestry points of the project. The version that supports Windows 8, 64-bit work, etc.
But this branching concept doesn’t help with agility, test management, feature management or anything but small projects.
A “topic” has a relatively short life time and is supposed to comprise a subset of changes, e.g. a particular feature, being prepared for addition to a branch. You might consider two types of topic, branched (that is, they are based on a specific revision of the branch they descend from) and floating (that is, they are represent a change set to the head of the branch they are descended from, whenever you refresh the working copy, the changes are shelved, the head is updated, and then the changes are re-applied).
The sole purpose of topics is for them to be merged upwards, e.g. when they’ve been tested and sanctioned.
There must be a VCS (aside from Torture-force, I mean perforce) that does this?