From what I know the FB16 got a new generation CVT which is different to the old generation 2nd revision "high torque" CVT used in the FA20 versions. This not only includes the belt itself but also the oil pump and forward/reverse gear structure.
The CVT in FA20 Levorgs is supposed to be a "High-Torque" variant while the 1.6l CVT can barely deal with the 250Nm torque of the FB16 engines.
On Youtube there are a few videos from MRT in Australia which seems to be working on modifications to the CVT to handle more torque. Not sure though if they plan to modify both, the FB16 and FA20 versions or if they focus on one only. As it stands now neither the FA20 nor the FB16 version can handle substantial more torque than the stock tuning.
From my understanding the FA20 version in Australia got detuned to 350Nm while it got 400Nm in JDM version. So it should be safe to give it a fair boost unless you exceed the JDM 400Nm.
The FB16 version however cannot deal with more torque easily so I personally wouldn't even try to put more than 300Nm on it without modification.
I also don't think the CVTs can be easily swapped which would allow FB16 owners to tune the engine and swap the gearbox for an FA20 high-torque CVT and peak out on 400Nm - well, not sure if that would make any sense on the FB16 engine either without heavy modifcations like changing rods, heads etc. which is kind of useless to do to a 1.6l engine. So you likely would be better of going for the FA20 platform at first place.
However this is just what I picked up on some youtube videos as we can't get the FA20 Levorg here in Switzerland anyway. But I don't think it would be an easy swap and CVT currently limits the tuning capabilities of the Levorg. Sure you can still do it but expect damages in the long-run on the CVT.
Given the fact our 1.6l FB16 pushes 250Nm of torque ranging from 1800 to 4800rpm I also see limited tuning potential even if you electronically limit torque. To stay within the limits you might provide 250-300Nm on a wider rev-band like 1500-6000 with a lot of effort. So you actually get more power output. But this would be a minimal gain for daily drives as CVT usually keeps the engine within low rpm on "normal" rides. And the Levorg wouldn't be my first choice for a track day anyway.
So I personally don't see much point in tuning here despite some academical research or if you just do it for the fun of doing it.