First of all, an it is important to remember that the Swirl Mastercard, Viabuy and so on are prepaid debit cards, not credit cards. The money loaded on to them is your money. A credit card works differently. You are spending the banks money and you pay the bank back when the bill comes in.
All pre-pay cards should work when booking accommodation on websites that debit your card immediately for the full cost of your stay, and pay the hotel on your behalf. Hotels.com and aerlingushotels.com are good examples. Booking.com works differently in that it just makes a reservation and it is up to the hotel to put through a "card holder not present" transaction if they so wish. Some hotels do and some don't. If they do try a "card holder not present transaction" it will usually fail with a pre-pay card. So stick to hotels.com, aerlingushotels.com etc.
Upon check-in, most hotels will ask for a pre-authorisation on your card to cover incidentals. This is where the difference between a debit card and a credit card hits home. The effect of the pre-authorisation on your debit card is to put a hold on some of the money that you had loaded on. So you have less money on the card than you thought. And the hold may not be released for up to ten days. With a credit card, the hold is on the banks money, and people who operate their card well within their credit limit won't notice the effect.
Car hire companies insist that your name is embossed on your card and that it matches your drivers license. As far as I know, Swirl doesn't emboss names so you can't use their card for car rental. Viabuy does emboss names so their cards might work. Revolut also embosses names. I have used my Revolut card in the United States with Alamo and in Ireland with Enterprise, Europcar, and Hertz. I usually purchase the Super Collision Damage Waiver to avoid a deposit of up to €2,000 being pre-authorised on my Revolut card. Just be aware that most car-hire companies say that they don't accept pre-pay debit cards so while Revolut is working at the moment, it may not in the future, leaving a possibility of being turned away at the counter.