Upgrade parts for beginners

[XStream]

As an absolute dnano newbie I'm looking for some upgrade parts for my Porsche 911 GT3. I would like to have suggestions on brands and types (the save choices), since there are so many different choices. I know that I will have to find out things by myself, but I don't want to buy every possible option that exists.

I would like to get the following parts:

New tires and wheels

I would like to have alu wheels and tires with a compound that is recommended for my track. I'm racing on the new kyosho dnano home circuit, which uses hard pvc (similar to realtracks?)

I'm a bit confused after reading stuff about alu wheels which didn't support stock tires etc. I didn't expect many different sizes of tires. Therefore I would like to get a suggestion on wheels+tires that match.

Bearings

any suggestion is welcome

Differential

Could someone explain what a differential actually does?
Which non-stock diff is the most recommended one?

H-plates

I guess this is an easy choice since they are offered in sets with different types. I'm planning to get onces that I can order together with the other stuff.

I know that I'm asking alot at once and that many things will depend on personal taste and racing style, but it shouldn't make much difference since I'm completely new to rc racing.