I have never used Paywithflash, but I saw that they released a new wallet and I was curious, so I installed it on my phone.
I was particularly interested in this by Pierre Corbin:
It’s the first mobile self custodial wallet that can trigger payments while in your pocket.
After installing the wallet, I decided to see if it could receive a small payment right off the bat. I'm interested in this because I'd love to be able to tell someone to download a wallet and then zap them 100 sats and have that experience be easy.
At first I created an invoice for 10 sats. When I copied the invoice to pay it with another wallet, I noticed that it was a Liquid invoice, not Lightning. Not sure if this was supposed to happen or not, but I assumed my amount was too small.
Next I created an invoice for 1000 sats. This worked and I was able to copy an ln-invoice and pay it with another wallet. The payment wasn't as fast as some of my other lightning wallets I've used. It showed up in Flash Wallet in about 5 seconds, but was listed as pending. I'm not sure how long it stayed as pending because it didn't update on its own. It only switched to paid after I tapped away from the invoice screen.
When it did arrive, I noticed that the amount was only 950 sats. It seems that the Breez SDK led to a 5% fee. I was curious about this (because it seemed high), so I went to Breeze Tech's documentation and found this page about end-user fees.
It seems that they way they are able to do this without lightning channels is that they use Breez's nodeless implementation that relies on Boltz swaps and Liquid. As far as I can tell this means Flash Wallet is good if you are a merchant who wants to receive payments over a several thousand sats, but may not be the best wallet if you are looking to do zapping on nostr or SN.
It doesn't look like they've posted their documentation for the wallet yet. When I click on getting started -> connect your wallet -> flash wallet I get a blank page.
It's cool to see new wallets starting up. It certainly looks nice. Hopefully they will get a little more documentation up soon, because I had to do a bit more sleuthing than I would have preferred to figure out what was going on. Ideally, I'd be able to learn a little about the fees directly in the wallet.