My understanding of the free server system is that experience rate is reduced but optional subscription increases exp rate to normal (or beyond) regular servers.
Its the same pricing plan eRequiem is going to do, free to play, but multiple levels of subscription that increase leveling efficiency, item drops, and available items. By all means they could have servers where you are required to pay a monthly fee to pay (and can't play if your account is unpaid), but the key is that when the game is free and obtaining higher efficiency is optional, you attract the free game players but still make subscription revenue... its a win/win for them.
My understanding is that the base rate is lower, but it could be improved to 1x or higher with a paid subscription. The cost of subscription from the sounds of things will be cheaper than regular pay to play servers. I think its a fairly solid subscription system, and has the possibility to work well.
On kRO main servers, storage space is 600.