-snip-
Have you used CC or DC? And which is more advisable to use CC or DC? Is there any difference in the fees anywhere when DC or CC is being used to purchase btc. How much time it takes to make a purchase, is the amount deposited in bitlish.com instant or it takes time?
For bitlish.com it does not matter whether it's CC or DC. It would matter to you as consumer, you might get more reward points when using CC instead of DC (depending upon your CC issuer) and then you can pay your CC bill after few days in next few months.
During this time you can sell your BTC and earn some profit and pay your CC bill with your profit too.
Deposit time should be instant whether one uses CC or DC. FX conversion should also be the same whether one uses CC or DC.
Once USD/EUR is deposited in your Bitlish account then you're able to buy BTC instantly.