I also have that bike and fitted the FSA threaded adaptor. No more creaks or clicks. I’m pretty sure the bottom bracket is a normal BB30, but there are 24mm reducers fitted to suit the Tiagra 24mm crank spindle. The bearing points on the crank spindle are offset from the bearing races. If you were designing something to creak, that’s how you’d do it.
The FSA adaptor is fairly permanent – it presses into place and is held in by glue (glue may or may not be supplied with the adaptor – the recommended one is some sort of epoxy (can’t remember the code number, but it’s in the instructions)).
No regrets here, it works very well.