Hello i need some help in my first SFF pc build (A4 h2o)

https://au.pcpartpicker.com/list/LQLV6B

For the power supply I have added ,

https://www.mwave.com.au/product/xpg-pymcore-sfx-850w-80-gold-atx-31-fully-modular-power-supply-ac94976

It said it is SFX , is that all I need to check or do I need to check dimensions etc as well.

Secondly on the cooler, is Atmos still a good option. Or is there something else I should be considering (slightly cheaper but similar performance) or Atmos ii which I can get for 50 more.. etc.

Lastly what other things I need to buy any cables? or extra fans . I am assuming thermal past for cpu? if so could you recommend which one.

thank you