This is sth. you can only decide for yourself. I, personally, would not like to have a server on an end-user home-connection. Usually you will not have a fixed IP and therefore use dyndns or sth. like this. Down-times of severeal are common als the promised uptime of 99% for most end-users (where I live) still means you can have >80 hours downtime a year… The good thing, of course is, you’ll have direct physical access to your server.
As for RAM, do not go for DDR 2400! Ryzen processors profit a lot from fast memory. Choose at least DDR 3200 CL16 (some people go even higher) becaus you will most likely not replace the ‘old’ memory when upgrading in the future but adding to it. So buying DDR2400 now is wasted money, if you ask me. You will want to use dual-channel mode for speed, so go for two modules. If I were you chose a mainboard with 4 slots, populate two of them with a 2x8GB kit now, and have the option do double the memory later on. (often then slots 1 and 3 are the different channels, with which you would want to start with)
Just my 2 cents. Have fun!
PS: The A320 chipset will not be able to run ryzen 5000 series cpus in the future. If you want to buy sth. now choose at leas b550, or if you’re fine with Q1 2021 you can go with B450 chipsets. Check the manufacturers’ website if they will offer support for the new CPUs in the future