First scratch build in ten years, talk me out of my mistakes

[Harbour]

After a decade of laptops and prebuilts I am finally doing a proper scratch build again, and the landscape has changed so much it may as well be a different hobby. Last time I built, air coolers were a personality trait and RGB was optional rather than mandatory

Rough plan is a mid range gaming and photo editing machine, prioritising quiet operation over absolute performance. I care more about the thing being silent under load than about ten extra frames. Budget is flexible but sanity is not, I refuse to pay scalper prices for anything

Before I start ordering, what are the mistakes people made getting back into building recently? Not asking for a parts list, asking for the traps. The things the spec sheets do not tell you until the box is open and the return window is closed