Mercedes won't be significantly worse (if any) than RBR and Ferrari in the technical section, I think. Their last PU update seems to have made a big step when it comes to accelerating out of slow corners and their rear downforce/traction also got better with the latest aero upgrades, it seems.
Let's see how Ferrari performs. They made a step forward on fast corners, but not sure about their performance on slow corners which they normally have been strong at.
I almost have the feeling that Mercedes might be on par with Ferrari in technical sections now. Both pushed with upgrades into the direction they were lacking performance at compared to their main rivals and now each of them will be favorites on tracks they weren't before.
Jokes aside, is it even possible to sacrifice performance at one area to get better at another like in case of Mercedes and Ferrari getting stronger on fast corners, but weaker on slow corners (and the other way around) as before?