i havent researched it much except that custom classes will be restricted in competitive playlists (is the competitive playlist like the “ranked” playlist from halo 3?). but what about casual playlists? (to my knowledge casual playlists are similar to halo 3 social playlists?) so whats stopping ever kid from spawning with a sniper and a rocket launcher?
You cannot spawn with power weapons.
ahh ok thanks! 
Primary starts are limited to the DMR, AR, LR, BR, Suppressor, and Storm Rifle. Secondaries are limited to the Boltshot, Plasma Pistol, and Magnum. The Firepower mod lets you have a primary as a secondary but that’s the highest you can go for starting weapons for custom classes.
No power weapon starts.
There is no “Ranked” or “Social” as such, but there will be more competitive playlists like Slayer Pro, but you will still have the more casual playlists like Grifball and Infinity Slayer.