How close were German battlecruisers to fast battleships?

On a scale from battlecruiser to fast battleship, where do the German battlecruisers sit?

They remain battlecruisers, though later German designs move closer to fast battleships; Derfflinger is still clearly on the battlecruiser side.

Derfflinger still belongs on the battlecruiser side of this comparison, while later designs move towards heavier protection and fast-battleship characteristics. Listed maximum speeds need separating from practical performance: Goeben is described as a nominal 28-knot ship designed for 25.5 knots and often unable to maintain even that figure. Seydlitz is singled out as the reliable 28-knot example, while the Derfflingers are put at roughly 26.5 knots. The proposed Mackensens depended on high-performance Parsons turbines for 28 knots. Obtaining that British machinery during the war was doubtful, weakening the apparent speed advantage of the later designs.