Server Lag

I guess it is because of the mob farms and the amount of players online per day plus the redstone contraptions. I will explain each one in a bit
First mob farms: lots of players (including me of course) make mob farms and especially villager farms. This leads to tons of breeders which are highly productive and gathering large amounts of villagers in at most two chunks. Personally due to the fact that my breeder was really productive(and after a bh announcement telling me to take control of my breeder) turned mine off. But there are some breeders(like the one in themodded's wilderness region) which are turned on and have tons of villagers in them. This results in tons of memory drainage and consequently in tons of lag.
Second the amount of players online per day: as we all can see recently a handful of new players keep joining the server daily. This results to almost every day the server to be full. I think that because the server limit is at 40 and almost always they players that are online are between 17-38 the server reaches its limits accorrding to memory usage. Therefore due to the fact that each player has his own region or his own builds it leads to memory drainage happening and causing lag.
Last but not least are the redstone contraptions: i am one of the players that use clocks and redstone contraptions. This leads in tandem with the point i stated before lead to lots of lag spikes. Its a common knowledge that redstone is something that can cause lag. So even though one of the most laggy redstone devices(the hopper) has a certain limit per chunk there is still a handful of other redstone devices(pistons especially the ones used in automatic farms) leading to lag.
All in all i dont know if my points are right or not or the lag is just due to some plugin problems but thats what i believe!
P.S. i forgot to mention about the amount of farms that exist using item transports with packed ice and water streams. Dropped items create major lag to the server and it is very hard for it to clear it. I personally have only two such farms. But there are players who have tons of such farms...

Well first same goes for me according to the player number. Second those players live in large regions with lots of contraptions and such staff. Therefore the lag is happening regardless the player number online.

Entities can take up as much processing power as a player can at around 30 or higher. So in this sense, usually when we have about 10 players on, we are usually taking up the same amount of computing space as about 25-30 players.
Minigames servers also load differently than survival servers. They have controlled areas that are loaded and entity lag is kept to a minimum. Player movements also have no need to be tracked. If our server was a minigames server, we could easily and efficiently house up to 60 active players without lag.
Our server is hosted in the US. Those across the pond will experience some latency issues. This is common and is not something we can address. Latency lag is especially noticeable for those who die from region pole warping. If you have died from teleporting, it is a latency issue, something we cannot control. Best advice in that regard is you would have to come stateside or ask your ISP if they can help in any way.
Sign shops create a lot of lag when people spam sell or buy from them. This is also something we can not address at this time as it would entirely spoil the server economy.
Other plugins are relatively passive and do not take up a lot of computing space on the server.

If you would like to contribute to the server and help fix the lag issues, you can donate to the server. As of this post, we have five patrons and thanks to them, we were able to upgrade the server capacity to where it is now.