I suspect it will be always firing on full power.
The A68 has the new Sony multi interface flash shoe, so needs a flash designed to work with this.
If you want a (relatively) cheap, light flash the Neewer NW320 is only £60 from Amazon, has twice the power of the 1800AF, adds bounce and swivel, and can act as a remote slave (but only manual power control in slave mode).
I use one on my A6000, due to it's small size, making it perfect as part of my 'travel kit'
It is also branded as Meike MK-320