Most PCIe Slots,

1. ASUS PRIME Z390-PRO: Features 6 PCIe, 2-16x and 4-1x and is compatible with Intel LGA 1151 sockets. 128GB Max, 4 DIM,
2. ASRock X399 Mining Master: Gaming. 8x DD4 - 128GB Ram Max. 3 PCIe all at 16x.
3. EVGA X299 Micro: Features 3 PCIe 2x16, 1x16 and supports Intel Core i7 and i9 processors. 4 DIMM 64GB Max
4. ASRock H110 Pro BTC+: Supports up to 13 GPUs, cost-effective, and reliable. 32GB Max, 2 x DDR4 DIMM Slots, 1-16x & 12-1x PCIe
5. ASUS B250 Mining Expert: Offers 19 PCIe slots, 18-1x & 1-16x. Max 32GB Ram DDR4.
6. Biostar TB250-BTC Pro: Supports up to 12 PCIe. 32GB Max 2 DIMM

Most Ram Capacity

1. ASUS Z10PE-D16 WS: (16 DIMM x 1024GB Max), 4 PCIe 3.0 slots (4 x16 and 2 x8). Multiprocessing x 2. Based on the Intel C612 chipset for Xeon E5 v3/v4 processors. Best one.
2. GIGABYTE MW51-HP0: 8 x 64GB or 128GB slots for a max of 1TB, 7 PCIe slots
3. Supermicro X11DAi-N: 16 DIMM up 4TB or 2TB (128GB per DIMM), has 6 PCIe. 2 x CPU. Based on the Intel Xeon Scalable platform.
4. ASUS WS C621E Sage: 12 x DIMM, Max. 1536GB, DDR4, 6 PCIe 3.0 x16 slots 2 at 8x, 2 x CPU.
5. ASRock X570 Taichi: 256GB total (8 x 32GB slots)
6. ASRock EP2C621D12-B8: 12 DIMMS 32GB per DIMM, 7 PCIe slots.
7. MSI Creator TRX40: 256GB total (8 x 32GB slots), also compatible with AMD Ryzen Threadripper CPUs.

More Choices, 128GB Ram

1. MSI MAG B550 TOMAHAWK
2. GIGABYTE B550 AORUS ELITE V2
3. ASRock B550 Steel Legend

1. MSI MPG B660 Gaming Edge WiFi
2. ASUS TUF GAMING B660-PLUS WIFI D4
3. GIGABYTE B660 GAMING X AX DDR4