Yeah, I think the level of secrecy over the first testing is a clear admission these new engine regs, which led to such weak engines that they had to create ridiculous moveable aero regs so cars wouldn't lose power at the end of straights, are absolutely terrible. I'm expecting this to be quite a clown show early on, which should at least provide some entertainment.
We'll have to see how it plays out, but i think the moveable aero will be awful for overtaking. Pretty much every type of formula car racing series understands that you need some assistance in overtaking due to the dirty air created by such aerodynamic cars. Indycar has push to pass, F1 had DRS. F1 already had issues with overtaking this year with DRS, and now they didn't just get rid of overtaking assistance, they actually went even further and made it significantly harder to overtake.
Moveable aero means even less slipstream on a straight because the wings will go to Monza-level and no car will have a huge advantage in the corners since they can all raise their wings. Maybe the limited engine power means teams will choose to deploy in different parts of the track and that could create some overtakes, but I doubt it. All these teams are going to identify the optimal places to deploy and likely have almost identical mappings, just like what happens now.
The only real hope for much overtaking is one or two engines being significantly more powerful than the others, but that's a bad thing because it means about half the field will be completely uncompetitive.