The Iris Xe uses a portion of system memory so with 64GB of RAM, that is completely doable. This list from the support page shows that GPU compatible with the 12th Gen i5/i7/i9 CPUs. Table 1. GPU—IntegratedCONTROLLERMEMORY SIZEPROCESSOR Intel Iris Xe Graphics (Dual-channel memory configurations) Shared system memory 12th Generation Intel Core i5/i7/i9 As for the 4TB SSD, it will run fine and be fully functional with the i5 CPU. The chart here shows no limitation based on the CPU.  
I'm looking at an XPS 9520 with an i5-12500H, Intel UHD graphics, 8GB memory, and a 512GB SSD. If I install 64GB of memory myself, would I then be able to use Intel's Iris Xe Graphics? Also, Dell's configurator says that the 4TB SSD requires an i7, a GeForce RTX, and 16GB of memory. Is there any reason why a 4TB SSD, if installed by myself, would be less than fully functional if I have an i5-12500H and UHD graphics?
The Compatibility of Customization Options