The HTTP uplink has no settlement built in, it’s purely used for development when you have a connector exposing ILP over HTTP. The Coil uplink doens’t do settlement either, but it requires you to have a Coil subscription. The fact that there’s no settlement on the Coil uplink means that you can’t use it to receive money (if you receive packets on it then they won’t be settled). Like HTTP, the Coil uplink is only intended for devleopment (if you have a Coil subscription it’s an easy way to get connected to interledger).
ILP over HTTP is actually different from the HTTP-ILP used in Koa ILP. In Koa ILP, an http request is made to an API who is the ultimate receiver of a payment (i.e. a codius host). That API is not your peer, though. You negotiate payment details and then send them money over Interledger.
With ILP over HTTP, the HTTP endpoint is your direct peer. instead of connecting with a websocket, you post ILP packets to them each in their own HTTP request.
So you could think of ILP over HTTP as an alternative to BTP (bilateral protocol spoken between peers), and HTTP-ILP as more of an alternative to SPSP (end-to-end protocol spoken between sender and receiver).
The naming for these protocols could definitely use some work to prevent this kind of confusion 
I was wondering is there a solution somehow to use somekind of dummy database (similar to five-bells-demo) that will work similar to the image proposed? And in that case would act as a different ledger.
Do you mean like running your own private ledger to settle over? I don’t think there’s anything like that right now, but if you want to connect over Interledger without settling on any underlying ledger you could configure your connectors to talk directly over ILP Plugin BTP (or ILP Plugin HTTP).
Someone from Kava Labs would know more about this than me. If I remember correctly there’s a functioning Lightning plugin, but I don’t know if there’s a useable lightning testnet. There’s definitely an ETH testnet you can use for the ETH plugin, but I don’t know how to configure it. Can anyone from Kava weigh in here?