It seems like you generally know what to look out for. I'd like to just pitch in and say that you shouldn't skimp out on a power supply. I remember there was a list floating around the internet (perhaps you can find it if you search for it) that lists different power supply models and their reliability. If you can find it, I'd recommend giving that a look before deciding on your power supply.

Also, make sure that whichever power supply you get is rated to handle the sum total of energy usage from the rest of your PC. I find that PCPartPicker has an accurate wattage calculator, so I would recommend plugging your build into there. My general recommendation is to try to pick a power supply where your estimated wattage is around 40-70% of the rated wattage of the power supply. (i.e., 0.4 <= estimated wattage / power supply wattage <= 0.7) Around 50% is the sweet spot of energy efficiency, and you definitely want to leave yourself some extra wattage for margin of error, in case of energy spikes or something of that nature. If you think you might upgrade to a higher-energy CPU or GPU in the future, I would recommend going for a higher rated wattage for your power supply (ie, nearer to 40% estimated wattage)

As for cables, you should be given cables from the motherboard and the power supply. Unless you have an excessive amount of fans or drives, you shouldn't need to worry about missing a cable.

As for the GPU, Nvidia basically always falls short in terms of price to performance. You'll have to consider whether you want ray tracing or CUDA, since Nvidia got those on lockdown. If you don't particularly care about those, then AMD is by far your best bet for price to performance. As for which specific model to get, I think a 7800XT might be a good start.

There's been a bit of a "crisis" recently about how much VRAM a GPU should have. Basically, in terms of raw power, I think a 7700XT would probably be fine for your needs, but it's only got 12 GB VRAM. Nobody can predict the future, so take this with a grain of salt. But my concern is that 12 GB might not be enough in the next few years. So I would suggest a 7800XT.

You can also take a look at AMD's previous generation, the 6000 series. The 6000 series nowadays can often be found for crazy-good prices, so if you're OK with some older technology, you can definitely take a look at the 6800 or the 6800XT.