I think Blackswan and Catfish gave sound advice. I have seen computers that were factory setups and run well on games. I think for gamers like you, Blackswan and others that are more discriminating, a custom build is probably the better way to go. You can probably get a better deal if you purchase your components from the same place and bundle higher end components like the motherboard, video card, etc...
As Blackswan said, airflow is important and serious gamers have had water cooling in their rigs as well. I would only add that if you go with a custom build, make sure the board supports newer processors and lots of memory.
I remember that others, I'm thinking Gary ( GT182 ) from Subsim, built or bought something that was an AMD Ryzen 8 core 16 thread CPU board. Today, the Ryzen is a 16 core 32 thread.
https://www.amazon.com/amd-16-core-p...core+processor
I don't think that has much application on games as programed games can't use multiple core as far as I know. Games can only use 1 signal path and in some cases, the CPU's that run many core like the Ryzen don't perform as well in games as a CPU with a lower core count but run at a faster speed. The Ryzen's may be better as I have never seen them run or read any reviews on them.
The other thing to consider is availability. With the current bottlenecks with shipping and trucking shortages and strikes fueling inflation, prices are being driven up.
Good luck with everything. Let us know how it works out as I'm sure many others are contemplating the same build and would like to know what you chose and how it worked out.