Whether you are a Reddit refugee (I am one) or just randomly stumbled upon Lemmy and decided to join lemmy.world, welcome to the Fediverse.
If you have been here for long enough and settled in and now finally feel comfortable with Lemmy, I highly advice you to move to smaller instances. I just newly left Lemmy.world to join Lemm.ee.
We need to capitalize on the decentralized nature of the Fediverse and Lemmy instead of having everyone joining one instance. This will benefit the admins of Lemmy.world a lot as they would not have to deal with such a high amount of users. It also leaves room for new users to join and have a good experience rather than an experience filled with server outages where they will give up on Lemmy.
You see the same activity on Lemm.ee, sh.itjust.works sopuli.xyz and reddthat.com that on Lemmy.world, with the additional benefit of higher uptime (less likely to get targeted as hackers want to take down the Lemmy.world)
Not in All. The traffic in all is proportional to the number of subscribed communities of an instance, which is roughly proportional to the number of users.
Lemm.ee, sh.itjust.works both have more that 2k users, sopuli.xyz, reddthat.com has 600 users.
With this amount of monthly active users, your needs for All are covered (most of the active communities will at least have one subscriber on your instance) except if you have very niche subs, which you would probably subscribe to by yourself.