I have a 2018 model Mac Mini i7 with eGPU (Razer Core X and Radeon RX 560). The computer has upgradeable RAM but it requires specialized tools and disassembly so I only wanted to do this once. I think once 64GB modules come around (i7 Apple uses in Mini supports 128GB of RAM max) I’ll be using Apple Silicon based Mac by then.
Original it has come with 8GB of Single Rank (1R) memory by Micron (2 4GB modules).
Theoretically 1R module should be faster than 2R.
I could not find a 32GB 1R module and installed Double Rank (2R) modules instead.
I am using Samsung M471A4G43MB1. So far no problems, I have not noticed any slowdowns due to 2R as I tested by creating a RAM disk and running Blackmagic Disk Speed Test. The system overall is more responsive under load as I was getting unresponsive episodes with 8GB once I opened too many things. From my experience get as much RAM as you can afford as that creates a little bit of future proofing. But even now I am using most of the RAM as I process footage from GoPro Fusion or edit clips in iMovie - I see not only memory being used by apps, but also Cached Files which greatly speeds up the feel of the system.