In the industrial world, we use 50 mV shunt resistors. Regardless of full scale amps, the shunt resistor will drop precisely 50 mV at full amperage. You would need 200A:50 mV.
To this we add a high side sense amplifier, perhaps buffer it with an op amp and then stuff it into an ADC input like those on the Arduino.
I'm not going to get into the AC side but basically, I would use a current transformer feeding a burden resistor then rectify the result and scale it with an op amp before stuffing it into another ADC input. We usually use 5A current transformers so, perhaps 50A:5A work. I have never used a Hall effect device. They may be a lot easier to use.
Be very careful with current transformers. Should the secondary become an open circuit, the transformer voltage will rise to a VERY high level. Suppose your CT had 50A through the primary and was trying to drive 5A through the secondary but the secondary resistance was approaching infinity. Ohm's law still applies so the voltage across the terminals tries to approach infinity. There are some limits but none are helpful.
https://openenergymonitor.org/emon/node/842I stay away from mains stuff. I'm perfectly content at 50V and lower - usually MUCH lower. My favorites are 3.3V and 5V. For the mains, I might just use a clamp-on ammeter connected to a logging DMM. I would definitely recommend this clamp-on approach for newcomers. I HATE mains voltages.