Yeah, it's still pretty early days with these engines I think, and it's hard to find much reliable information out there. From what I've learned so far, remaining low-effort (and non turbo/ethanol) upgrades at this point are TGV and EGR deletes and a header (also adds support for an external wastegate, but is super spendy) for maybe an extra 20kW and no need to change anything other than the tune.
Ethanol and a flex sensor setup would give maybe an extra 40kW, with the factory injectors and fuel pump up to E30, and a replacement pump with more than that. With all of these mods and a FMIC, and maybe an intake for a handful of extra horsepower, I could be looking at anywhere from 270-300kW. I could get better numbers with a bigger turbo (but not a whole lot of options there). Either way, anything over 250-260kW means the possibility of throwing a rod on the factory internals.
Torque comes on really hard and early thanks to the tiny twin-scroll turbo and its low positioning, but it also starts running out of puff above 5000RPM. That 4500RPM dip seems to be almost universal on tunes of the FA20DIT that I've seen. No idea why, but even the NA BRZ has the same dip there. When it was new it was really, really noticeable but is much less so now.