The modded server still exists if you want to play on it 🙂 But I appreciate there's fun in the challenge of figuring out your own 🙂 I remember Voizdev on youtube having some good tutorials on starting and joining servers.  They may be out a little out of date now but I'm sure they're still relevant.  It's more connecting, joining etc. though rather than hardware.  Hardware wise, Minecraft is pretty easy to run so just go with whatever the best hardware is that fit's your budget.  Some general comments though, Minecraft is still terribly multithreaded so benefits massively from fast single cores over high core count CPU's.  RAM, fast RAM is great but total pool of RAM is more important than speed and even for the heaviest of modpacks I don't think we ever went above 8Gb but we probably pushed that limit a few times.  Storage, less of a consideration so really any SSD/NVME would do.