The maximum ram you will need is about 16Gb ram. 32Gb is overkill unless you plan on running multiple servers and maps larger then 8K.
The connection you have is gonna help alot. i found 7dtd needs a fast network if you want to do more intense stuff like mega zombies.
4 cores helps a lot but 2 will do for a basic server.
HDD is ok but ssd or as i do it NVME is best.
also depends if your running linux or windows.
16 - 20 players if the best you can expect with minimal lag for everyone, with the highest pinging player dragging the entire server down.
if you do 8 players as recommended, any set up will do.
IF you want above 20+ players that network speed is whats gonna help a lot.
keeping in mind your home network and all devices are gonna cause issues the more that are connected.
From my personal experience over the years,
7 days to die will punish everything you use a lot the more players that connect at the same time.
a high speed cpu in the 4.0 -5.0 ghz range helps when used with NVME and a 1 GBPS network.
DDR 3 ram is fine but like in everything newer is better.
I can only speak from what i have done myself over the last 8 years, and i am obsessed with high quality and high speed.
so, if you have 8GB ram a hdd and that 1 gbps network, you will run just fine.
just restart the server often every 4-8 hours making sure you manually save it before each restart.
just keep in mind the more players that you want to host the more power you will need in terms of hosting specs.
I have seen 7dtd use as much as 65% cou on a ryzen 5800X and anywhere from 8-25Gb ram and at least 2-5 MBPS of network. (1 GBPS network)
this is with 200+ zombies and a 8k map with 25 players connected at the same time. there is lag yes but it is minimal if your host can handle that type of load.
however at this point, finding players could be difficult right now.
This is my opinion and i am sure others will chime in soon, and call this all hog wash lol.
