I have player the original arma (operation flashpoint) and Arma3.

And while there is a ton of depth, you can ignore part of it if you want to play more casual.

While you can know all the details of a weapon at a ridiculous level, you do not need to know them to finish the campaign.

For multiplayer I can’t help as I’ve never played it. But I suppose it would depend on the server and which people you play with.