>Are they able to have their own accounts/avatars on one system ?

Yes.

>Is 4g speeds enough to get the online version ?

Couldn’t say, but probably.

>Is the disk option better ?

In my opinion yes because it allows you to have options. You’re not committed to only downloading games. Having the option of either is great. It also allows you to resell a game if you don’t want it anymore.

>I'm am totally clueless as back in my day you got a physical chip for storage and could store many versions of the game on each chip or have different chips each .

Definitely not the case anymore. Everything is on a big storage system built into the console.

>Thanks for Any tips and advice ye can offer.

Both Xbox and PlayStation have subscription services that allow you to download a library of games at will as long as you are paying for the service. This can be a good way to offer a lot of games to play without buying hundreds of games.

They also both require an online subscription to play any game that isn’t free. And every month there are games offered to download and keep, also only playable while the subscription is active. So make sure they at least add those games to their library so they can be played if they want to.

Oh and if this isn’t already common knowledge, be very aware of monetary systems in certain games. A game like Fortnite will offer a seasonal pass that can be leveled up, and rewards are given at each level. On top of that there’s a store that rotates stock daily that offers skins and items for real money. Many games offer this stuff and you may find your kids asking you constantly for money to get this stuff. Or they might be finding ways to buy it without your knowledge. I don’t know your kids, but just take this as a warning that some games, even free ones can end up being an endless pit of buy buy buy more more more.