I think the jackpot makes sense. It is a bit over powered, but it is available and if we can make it standard, it would solve that issue (out of stock, many versions of the pen board).
In my table I used 60 pixels per meter. I like the ws2815, which are individually addressable and are 12V. The wiring is a little bit more complex, but the power only needs to go to one end. The only ones I would definitely watch out for are the ones that keep 3 pixels per controller, so they are only controllable in triplets.
WLED is the way to go. FluidNC won’t be able to match the beauty of WLED anytime soon. And an extra ESP won’t break the budget. There are some other good (I think) design decisions baked into that table, like putting the leds a bit further from the edge.
The only active electronics are the controller and the motors. They are all on one side. As long as you have a smooth running table, you can turn the current way down. So I don’t think heat will be a problem at all. You haven’t mentioned the size you are looking for. If it is a dining room table, you might need to keep the current a little higher, but it will also have more air to cool it.
The bottom plate can’t have any midspan supports. I think glass is best for this. Any thickness of glass that can not break over the span you are looking for is a good thickness. I bought ikea shelves for my recent table. My counter top build uses glass tops from some end tables. I used 3/32" hardboard and it sagged quickly and the magnet scraped in the middle, which sucked.