The focus of the new IG dex is troops and so is the only information I have regarding new Dex.
First of all Guard are now 4 points each, but this is the "Ground level" guard so to speak. They can have no Special weapons or heavy weapons at all, in all respects they are the new conscripts but with normal guard stats.

There are several types of Platoon as we have already heard, Heavy Weapons, Forward Team, Armoured Devision, Airborne
In addition, each platoon is able to include 1 supporting unit, and this will NOT count towards the FOC.
The supporting unit varys in accordence to how its platoon is organised.

Heavy weapon platoons may take 3 heavy weapons per squad (10 man squad) but no special weapons, these is a points increase per guardsmen but he didn't reveal these. The heavy weapons platoon may take a Fire Support Squad or a Standard Leman Russ. There is additional heavy weapons being given to the guard which are only avaliable in this Fire support squad and not in the main platoon squads.

Forward Team is able to take 3 special weapons (Flamer, Melta, Plasma, GL) but no heavy weapons, in addition they gain Infiltrate. Their supporting units include Veteran Squad and Sentinel Squad. The Veteran squad also gains Infiltrate.

Armoured devision is mounted in Chimeras. They can take a combination of either 3 special weapons or 1 heavy and 1 special weapon. Their support units are Leman Russ Battle tank and Veteran Squad who must also be mounted in a Chimera.

Airborne I was not given much information about but I am guessing it is deepstrike and probably something revolving around Storm Troopers and Valkarey.

The reason Leman Russ are being included in the platoons as they want to push it being the main battle tank of the Imperial Guard and have it represented so.