I've got 12V / 400mA power supply for my Wemos D1 R1, and I'm using VIN output(I need 12V for led strip). I need to change this power supply because of color, and I can't find similiar with the same parameters. The question is - Is power supply with 12V / 1A - 2A safe to use?
With very few exceptions, electronic devices only draw as much current as they need, limited by their resistance.
The current rating on a power supply is the MAX current it can provide before the voltage drops. Having a higher current power supply may waste energy, but won't hurt anything.
According to Ohms law, V = IR
Where V = Voltage I = current, in amps R = resistance, in ohms
(voltage = current times resistance.)
Or, solving for current:
I = V/R
current = voltage divided by resistance.
So if you have a 12 volt power supply, and a 100 ohm resistor, you'll get 12/100, or 0.12 amps, flowing through the resistor.
I am a bit confused you state: VIN output, that is the voltage input to the onboard regulator. For the power supply use one of the same voltage but capable of more current. Current is the maximum a power supply will give reliably. Current is the current needed by a load so if the load is less then the source and the voltages are the same it is a go. The answer is yes either is ok but be sure you have enough current from the power supply + some to cover all of the LEDS.