Is there any rule on what redstone project does the server allow? I'm mainly concerned that whether server ban certain type of contraption because of too much load? For example: large scale melon farm using bud switch. a lot of periodic timer in large scale (for some random purpose) Given that I'm not intentionally trying to lag server, I just want to build some fancy redstone for fun. A separate question is that for melon farm example, could it also be asked to be removed by moderators if it causes a lot of noise to my neighbors?
Large scale melon farms are perfectly acceptable. The rule mostly stands against redstone clocks that constantly update and spam fireworks or item drops.
Nope I have once built a redstone parcours, with loads of different always extending and retracting pistons, etc, I didn't knew that those clocks wern't allowed, but it didn't get removed, I can still remember bigdavie just set all my clocks off and asked with a sign to make a system that only activates when someone is playing that parcours, so, shortly, nope. A think I will warn you about though is that the redstone mechanics are a little bit different in EMC though, I don't exactly know what, but quite alot doesn't work. oh, and if you want to share some of your redstone creations, I've made a bautifull redstone thread https://empireminecraft.com/threads/the-redstone-thread.67833/
There are some specific changes in comparison to vanilla, and some redstone blocks are included there. You can check the technical changes wiki page for a full overview. In short though: hoppers are slightly delayed.