Question(s) about cases and power supplies

Hello all,

I'm a fairly serious computer enthusiast planning to assemble a new PC
from scratch within the next month or two.

I have certain cases in mind from the typical brand names (Apevia,
Cooler Master, Thermaltake, etc.), and I want to go with an aftermarket
power supply (I've learned based on people's reviews to not use the one
that is supplied with the case).

How will I know for sure that the power supply I choose will have
enough of the right types of cables to properly supply electricity to
everything on my motherboard and case that needs it (cases nowadays
seem to have a lot of extras, like temperature readouts and bright blue
LED lights)?

Also, I've seen power supplies differentiated as ATX, ATX12V, etc.
What exactly is the difference? (I at least know that ATX is the form
factor I'm going with.)

Any help would be appreciated.

Thank you.

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