I do not know what conversion rate will be, how much they will take the cost for the above conversion?
I'm not sure. I went on to Bitrefill to check, but all four methods mentioned in the OP have disappeared. I guess they have removed them while they work to set them up properly. Having said that, Bitrefill's exchange rate for giftcards has always been pretty reasonable, in the region of a 1-1.5% fee, and with the 2% discount they offer for using Lightning, sometimes I can even buy giftcards for better than market price. I would be surprised if their exchanges rates for these new payments methods were vastly different.
I don't know if it is beneficial for you, but it is completely against me. I can even save that 10% cost on P2P transactions.
At the moment, I always trade peer-to-peer if I need to change bitcoin in to fiat to spend somewhere, which usually works out very close to feeless. However, it can be difficult to organize a trade quickly if I am in a hurry for any reason, or if I am not at home and see something I want to use some bitcoin to buy but have to pay in fiat. With that in mind, I would be great to have a simple, non-KYC method such as this to quickly turn BTC in to fiat that I can then send to another party. I suspect the biggest flaw here is whether or not the other party will accept any of these payment methods.