3 5 2... is it working?

The controlling possession element in that formation was fine for 70 odd mins against Brentford (maybe by design as Brentford tend to concede possession to stay solidly compact), it's the lack of creative quality that's the main issue.

With Werner in a 2, no...shouldn't be starting as the central outlet but no-one wants to hear that home truth.
Technical deficiencies and limitations are too great to work with Lukaku, a handicap (needs a more technical player alongside him in a 2, had that at Inter with Lautaro Martinez).
Lukaku alongside Kai Havertz would be suitable, to my mind.

Another one is Azpi as a wing-back with the onus to create, problematic.
352 will work with the right personnel in forward position and at wing-back.

However, the inverted wing-backs idea that Tuchel deployed against Southampton in a 343 looked the part. Should be seeing more that.

Lukaku up top with Kai should be put to the test at some point.
They'll compliment each other well.

Maybe not against Malmo, as Lukaku needs to be rested.
Kai has to start that match.

The problem with 3-5-2 is that we need a player like Zola to make it work. We have too little creativity and we are playing too much for counter-attacking opportunities. We've stopped creating the chances for Lukaku because if it's not counter-attack, possession is slow and laboured.

Our strength last year was our pragmatism - our ability to play both with and without the ball with seemingly little importance. I would hate to see us go down the Mourinho route and just defend and counter as our football has often been good under Tuchel. We need to start controlling games again and creating chances.