Question about Supermicro A2sdi-4c-Hln4f

1) 288pins or 240 pins. Important, especially as some information is missing on 2x8gb or 4x4gb for 16g. It seems to depend on the type of memory, RDIM, UDIM in DDR4. But I'm probably wrong. Excerpt: Memory Capacity 4 DIMM slots Up to 256GB ECC RDIMM, DDR4-2133MHz; Up to 64GB Unbuffered ECC/non-ECC UDIMM, DDR4-2133MHz Memory Type ECC/non-ECC DDR4 RDIMM Unbuffered (Operating speed up to 2133)2400/2133/1866/1600 (Operating speed up to 2133) DIMM Sizes 4GB, 8GB, 16GB, 32GB, 64GB Memory Voltage 1.2V Error Detection Corrects single-bit errors Detects double-bit errors (using ECC memory) On-Board Devices Then comes the super blur with the documentation: The A2SDi-2C-HLN4F supports up to 128GB RDIMM or 32GB ECC/Non-ECC UDIMM DDR4 in two memory slots, two DIMMs on single channel at up to 1866MT/s . The A2SDi-4C-HLN4F support up to 256GB RDIMM or 64GB ECC/Non-ECC UDIMM DDR4 in four memory slots, two DIMM Per Channel (DPC) at up to 2133MT/s. The A2SDi-8C/8C+/12C/16C/16C+-HLN4F support up to 256GB RDIMM or 64GB ECC/NonECC UDIMM DDR4 in four memory slots, two DIMM Per Channel (DPC) at up to 2400MT/s. Populating these DIMM slots with a pair of memory modules of the same type and size will result in interleaved memory, which will improve memory performance. From a vendor: Compuram.biz/memory/supermicro/motherboard/workstation-server/a2/a2sdi-4c-hln4f-a2sdi-8c-hln4f-a2sdi-8c-hln4f/16gb-00-x8df3.htm 2) This power supply is fine because I already have a mini-itx box: https://www.digitec.ch/fr/s1/product/intertech-unite-dalimentation-externe-connexion-externe-120-w-alimentation-pour-notebook-13914783 3) This adapter also with power supply and card: https://www.digitec.ch/fr/s1/product/intertech-mini-itx-psu-nas-dcdc-cables-dalimentation-interne-pc-15658837 4) Card with processor too? ! AFTER ! Suggest me memories for a 2x8gb if it's possible. I'd like compatible memory, not expensive RDIM, and it's not a server either.