As for your question about what troops to use. From a fluff perspective you can do just about anything, but a few ideas:
- Mechanized Infantry: would make sense from a fluff perspective; if the troopers are in Chimeras they can keep up with the tanks if they need to redeploy. They are a bit expensive when it comes to the gameplay side of things, and I haven't tried them myself yet. So I can't say if they are worth their points.
- Tempestus Scions: having some stormtroopers drop down from the skies in support of your armor also sounds pretty fluffy. You could also put a couple squads in transports and deepstrike some other squads. I often use stormtroopers alongside my tanks: they are really flexible in their deployment and the higher ballistic skill means they can use all those fancy special weapons to great effect.
- Infantry on foot: this is the Imperial Guard after all.. the infantry could have been moved in by larger transports before the battle, or perhaps they just march along whilst the tanks follow them about. Infantry squads are cheap and work well enough if you support them with orders and other buffs.
- Mix & Match: it's your army after all; do what you think is cool. Maybe there are 20 regular infantry men that are assigned to guard your tanks, and a squad of stormtroopers that was sent by high command to take out an important target on the battlefield. Or perhaps there is an Armoured Fist platoon attached to your Armoured Company. Or maybe your tanks are called in to support an infantry company, or a strikeforce of scions, etc.