Since Mercedes previously introduced some front suspension changes to W14 and W14B, front wing is discussed already in detail, rear wing is old spec and we haven't seen beam wing and diffuser - I will briefly focus on a couple of bodywork details. Overall, I see nothing but clear and unquestionable improvements of sidepods and engine cover!
The undercut g-line is quite clean, undercut throat is about the same as AMR, McLaren and Ferrari. On the other hand, the bottom side of the inlet is a really lovely solution in my view. For a team that can afford slightly smaller side inlets this might be the best solution overall. Basically, the "vertical" area near the chassis is part of the inlet and so you "take away" the inlet surface from elsewhere. This allowed them to narrow the inlet overall, reduce the local drag on the outboard section of the sidepod and potentially improve the flow behaviour in yaw in this area, ie prevent separation in adverse conditions.
At the same time, if you have a straight horizontal inlet this same inboard area would feature the most pressurisation, ie drag, so they've said - ok, we have drag there anyway, let's use it as inlet. Another thing is - they do a bit of boundary layer clean up at the same time. I'd say this solution is inspired by their launch-spec W14 inlets and some advantages it offered. Finally, they combined the horizontal and the vertical part with an arch which has a natural curvature to propagate a bit of outwash as well as provide just enough pressurisation to deal with the front wheel wake. AMR, McLaren and RB are now committed to different solutions, but I think Ferrari will definitely want to thoroughly examine this kind of geometry.
I love to finally see again the coke-bottle shape of their airbox, must be some nice pressure recovery there. The engine cover shelf outlet looks so much better and less obstructive than W14 B solution and I am very grateful to Mercedes we won't have to see that abomination any more! The rest of the engine cover in the rear seems as narrow as last year, so no complaints there.
Mercedes has now taken out any bodywork that might be too clever for their own good out of the equation and replaced it with refined and beautiful solutions. The car is pleasing to watch no doubt and the top side bodywork should do its job well and shed a decent amount of drag. I expect their performance to now fully depend on floor performance and how well the suspension is working with the floor itself. The same will likely apply to all Top 5 cars, if not all 20 cars on the grid.
