Minecraft Pocket Edition Realms cross-play with PC or Mac? [closed]

Solution 1:

There are currently two version branches of Minecraft:
the "Bedrock Edition" for iOS, Android, Windows 10, PS4, XBOX and Switch,
as well as the Java-written Java Edition for any Windows version, macOS and Linux.

Both are currently in further development.
All Bedrock Edition players can only engage in crossplay with other Bedrock Edition players.
All Java Edition players can only engage in crossplay with other Jave Edition players.

A Minecraft Realms subscription is limited to either the Bedrock or Java branch.
This is because the Java and Bedrock edition are different in enough ways that they can't smoothly interact, and that worlds from one can't be used in the other.

For the Java Edition, a feasible alternative to Realms is setting up a self-hosted server on a computer of your choosing.
Both Editions allow players to open up their game to users in the same LAN, limiting multiplayer to local play.

For both Editions, there are publicly hosted Servers.
Some of these allow Jave-Bedrock crossplay, but that's always implemented by the server owners and can limit the possibilities on that server.

As for Size and other differences, I can't help, but point you here: https://minecraft.net/en-us/realms/faq/