I am the new coming for this area. Trying to buy some carbon fiber materials but being confused about so many options.. what is the different between these two and how to choose it based on the application?

If you are looking to do "out of autoclave" pre-preg then you will need the Easy-Preg Surface Layer PrePreg Carbon for the surface layer to help get a good cosmetic layer. The backing layers are made up of the Vari-preg pre-pregs but typically for most none structural parts a common layup is one layer of Easy-Preg backed up with one layer of Vari-Preg430g 1.27m Wide giving a total thickness of 0.75mm.

I recommend you read our Beginners' Guide to Out-of-Autoclave Prepreg CarbonFibre and watch our tutorial videos as it explains all the basics in detail and should make it clear how the layers work.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I dont want to be rude and I always encourage people trying stuff, but prepreg is not the easiest thing to start with... 

I have watched this video https://www.easycomposites.co.uk/learning/how-to-make-complex-multi-part-split-moulds 

It wasn't an autoclave oven that was being used, but a conventional electric oven with vacuum fittings incorporated

If my rough conversion of the 42.5 l/m is right, then I think that would be around 1.8 c/f per minute displacement, though I'm sure someone will be along soon to correct that if I'm way off.

As already stated, the smaller of the two EC pumps is more than capable of handling all but very large pieces in a reasonable timeframe. It would still work on even large vacuum bags, but would take a lot longer to evacuate the air than a pump with a bigger capacity.