The Mister itself won't pull even 4 amps at 5 volts, no matter what, because of its overvoltage and overcurrent protection circuitry. You can go bigger than the GST25A05-P1J, but the only reason to do that is if you're using a Y connector and routing power around the Mister. (which some USB boards do). If you're connecting to the Mister only, you could provide a thousand amps and it wouldn't change anything, so spending more money won't provide any benefit.
You can buy anything that provides 5 volts and at least 4 amps on a 2.1mm wide by 11mm long barrel connector, tip positive/ring negative. The Mean Well is just known to be a good adapter that works on pretty much any country's power. Give it at least 100V, and keep it at 50C or under, and it will provide a nice steady 5V4A.
Note that it doesn't come with a mains lead. It has a socket like a computer power supply, so you have to provide your country's wall-plug-to-computer cable. That's why it works anywhere.
Again: if you're using a USB board with a Y connector mains lead, rather than pulling power through the Mister board, a bigger supply can provide more power to the downstream USB devices. If you're really loading that hub down, that can be a consideration. The Mean Well doesn't have a power switch, so if you're routing around the Mister, you can't use the digital board's switch to power everything off. You have to unplug the adapter, or add an inline switch. Use an AC switch, instead of on the DC side, because many DC switches are lousy quality and will reduce voltage.
It's pretty common for adapters with the right voltage and plug to be sold for use with Christmas lights, and getting a 6A or even larger supply is not difficult. The GST25A05-P1J is just a default option that will work for most users. If you don't know you need something different, and particularly if you don't want to think about or research anything, you can just buy that one, plus possibly a local computer power cable.