Yeah I have what Jim Craft is experiencing. It's not as much as him on my realm, but I do experience times where it's unbearable.
I've played on my realms for 2 months and it stayed fine but recently is has had immense lag even with two or three players on it at a time. I have never had the full 10 players on but we were planning on doing the ender dragon fight and I hope this issue gets fixed before that because at this rate, I don't think realms can handle 10 people even though it should.
In a typical Java Server, having more people on does make it laggier and even if you can hit capacity of the server, doesn't mean you should since people will be very laggy. But because this server is hosted directly from Minecraft Bedrock so the full capacity of 10 people is what I should be able to play!
I hate the be this one person but this issue has been out for 7 months and we haven't had a single mod actually talk to us about what is happening to the realms. Please if any mod sees this comment, respond with anything and if you can, send out an eta of when this will be fixed.