there are a variety of different upgrades you can get, mostly the upgrades have to do with tunability. adjusting how hard and what RPM you want the the shoes to grab.
aluminum will grab harder, but at the tradeoff they are more expensive compared to the carbon shoes, and they will build deposits into the inner side of the bell.
carbon won't build the deposit, but have a tendency to wear quicker, and are cheaper.
for this tradeoff, it is popular to run 1 shoe (for 3 shoe systems) or 2 shoes opposite each other ( for 4 shoe clutches) as composite and the remaining aluminum.
your Losi 8ight should have been a 4 shoe already, though i dont remember if the earlier ones were 3 shoe or not. (might be best to confirm)
spring thickness ranges usually from .9 to 1.1mm thick to change the RPM range at which they will grab. thinner will engage sooner, thicker engage later.
if yours is in fact the 4 shoe, i personally would start with getting a pair of aluminum shoes to replace 2 of the carbon ones with.
though there are many other high end brands that have more adjustable or tunable ones, like Reds, Protek, etc.