The amount of RAM allocated to each server varies by the amount required to operate efficiently. Did you have an actual support request that we can help you with? Otherwise I will mark this thread as done in 24 hours. Thanks
Servers usually don't need more than the client. The main difference are the textures (client) and plugins (server), in our case they weight out each other (in case of vanilla textures).
Why not? You don't use textures on server, so you can load server with older modpack with just 300 mb (tested it).
No, actually you have to just hold loaded and preloaded chunks. With 300 mb you can startup the server with all the mods loaded. 8 gb should be enough if you don't have bugs eating ram or players doing something stupid. I doubt that you need 64 gb for Civ, when you need 8 for infinity.
In my own opinion 64gb would be overkill for any server to host any mod pack, the server side uses the same or less than the client side so I would say the server should be able to do 2gb-4gb but having 8gb-16gb wouldn't hurt.
Seeing as the question posted has been answered, and there are no further support requests in this thread, I am going to go ahead and make it as done. If in the future you need further assistance, please don't hesitate to make another post here, or ingame with /ticket. Thanks and happy playing.
In fact, dedicating too much ram to java applications has negative effects with its gc. If your computer has a lot you can try it