I know and understands the merits of bedding an action into the stock.

What are the thoughts about also bedding the first inch or two of the barrel chamber?

I also read that quite a few rifles benefit from adding 4-5 pounds fore end pressure on to the barrel.
Is there a difference here between thin sporter type barrels and thick, fat ones?

By adding fore end presure, free floating is eliminated. so what is gained here?

I don't find any difference in bedding under the chamber or not. It's a place where epoxy flows and so most folks leave it. I will say that if you are going to leave in under the chamber area, that you at lease make sure it is ends cleanly and uniform. Having more epoxy on one side than the other looks bad.

Unless you are hand fitting the barrel to the channel from scratch, you won't know for sure where and to what extent the forend bears on the barrel. So, I would recommend that you free float the barrel first to remove all contact, and then try the gun while it's floating to see how it performs, then if you decide later to add pressure, you will be starting with zero stress on the barrel. It gives you a good neutral place from which to start so-to-speak.