It very much depends on your use for it. My use (in terms of software I run) consists mostly of a memory-heavy IDE (runs on the JVM), somewhere between 1 and 10 VMs, a bunch of Terminal tabs, and a handful of Safari tabs.
I needed a "stop-gap" solution when my ageing MBP17 started eating fans at a rate of 2 a year, about a month or 6 weeks before the 2018 event where the Mac mini was released (I was expecting an updated iMac, and planned to get one).
So I bought an off-the-shelf base unit (6-core i7, 16GB, 256GB), knowing it would be my primary driver for a short time, and then later would become a "spare" (if the desktop is unusable due to fault/upgrades/etc) and "travel" machine.
In this scenario I already knew that I'd be using an external SSD (so I can take my work from the desktop to the laptop with zero fuss) so the space was not a huge issue for me.
If it was my daily use machine, I'd definitely have maxed out the RAM and probably upgraded storage to 512GB.