Don't forget Visa/Mastercard fees can be 1-2%, with American Express being even higher... On lightning I pay a lot less fees, the only thing is that in fiat the fees are hidden within the retail prices so they don't feel as bad 😅
With the architecture described for Blitz, you’ll have to pay Boltz swap fees or possibly channel opening fees. Also, sometimes swaps fail and sometimes your channels get forced closed. Custodial lightning is cheap for users. Self-custodial lightning isn’t, but I think that’s okay as long as it’s not hella expensive 😂.