There's an argument for a 12 core/24 thread CPU given all the different usage and types of usage (and your considerable budget).
Looks like you might need/would benefit from quite a bit of storage. Those NVME M.2 SSDs are fast and not too far off the price of regular SATA SSDs now.
For motherboard a cheaper one around £200-ish would do but those just have 2 x M.2 slots so specced a good option with 3. Really when it comes to 3 x M.2s and well-built boards it (arguably) now comes down to the MSI X570 Unify or the more expensive Gigabyte X570 Aorus Master, so take your pick, or sacrifice a third M.2 slot for something cheaper like the Gigabyte X570 Aorus Elite.
You may or may not benefit from 64GB RAM. I don't want to overspec there and would suggest starting off with 32GB. It will likely be plenty. If you find scenarios using absolutely all the 32GB then you can add two more sticks in future. That Crucial 2x16GB 3200MHz kit is currently very cheap and it overclocks to 3600MHz very well (Micron E-Die). The red kit is currently the cheapest (there's white and also grey).
I've specced a quality 1000W power supply because you mentioned SLI, however these days SLI (NVLink now) is going out the window in terms of widespread support for it. To quote from a review website (Tweaktown):
Don't expect all games to have great scaling (especially at 1080p)
Don't expect all games to work with multiple graphics cards
Synthetic tests kick ass to show you the CAPABILITIES, but do not translate into real-world gaming
4K in the right game, makes GREAT use of two RTX 2080 SUPER cards
Read more:
https://www.tweaktown.com/articles/9070/nvidia-geforce-rtx-2080-super-nvlink-benchmarked/index.html
So you could scale down to a 650W or 750W if you prefer.
The 2080Ti doesn't make much sense for the money. Would suggest capping GPU choice at a 2080 Super. Next year there'll be faster cards than 2080Ti, and the year after that, and so on. It just doesn't offer enough improvement.
No monitor yet, thinking best to focus on discussing the tower with the components first, then we can get to talking about the monitor to cut down on information overload.
Here's a similar spec with all the parts from OcUK, with the Aorus Master motherboard and a 750W PSU instead:
My basket at Overclockers UK:
