There are loads of old posts about based around on similar topics to many of your questions and I'd advise checking them out when you get the chance. The 4 incinerator squad in a landraider is a bit excessive but I love the idea. Not many squads get that many templates. However, if your looking for template fun (and let's face that's what the inquisition forces do so well) a unit of stormies can have 2 basic flamers and a Sargent with an incinerator (you could use an elite inquisitor here, they have one more wound but use up an extra elite slot and give away one more kill point).
Deep strike grey knights is something you never see on these forums. The reason for this is that they are essentially the same as basic squads but can't claim objectives, making them far worse in any other mission than annihilation. As for terminators, LRCs are really good for these guys but it will depend on the rest of your forces. Deepstiking them might save you allot of points. You'll probably notice that allot of the DH lists on this forum use a grand master to lead them. That's because he's really
good in combat and his cost feels reduced when you don't have to take the compulsory brother captain for an elite choice.
As was mentioned before, dreadnoughts are definitely worth having for a GK list but as you said you will be using a fair amount of IG, you might not need them. Landraiders can be nasty, especially if you take more than one. Teleport homers are a good thing to have if you're deep striking terminators but they can also be good if you use daemon hosts as there teleport power allows them to utilise them.
As for paint scheme for inducted guard I'd keep it faily simple with a little extra black to bring out the more sinister element of the Inquisition. (A radical inquisitors inducted guard can be a truly sinister thing. Far more scary than anything the dark eldar or chaos can muster).
Play around a bit and keep tabs on the chat around this forum and I'm sure you'll soon come up with a style that suits you.