Which one to use: 搞笑 vs. 攪笑 and 搞亂 vs 攪亂? For "amusing/funny," CantoDict lists these two variations: 搞笑 and 攪笑.

Similarly, these two words are listed as variations of each other for "to confuse, to mess up": 搞亂 and 攪亂.

In Cantonese they are pronounced the same, but in Mandarin, they are pronounced differently.

1) Which should be used for each meaning? Are both variations interchangeable or is one preferred (for both Cantonese and Mandarin).

2) Are 搞 and 攪 interchangeable?
The two words have different meanings

搞 is to do something in a very generic sense, with mostly no attached meaning. 攪 is also to do something, but it implies making a mess and sometimes with the intent to do so. 攪 have another meaning as mixing.

In particular cases, 搞笑 is used in mandarin but not 攪笑.

搞亂 and 攪亂 both means to mess up, but 攪亂 implies the entity who does so have the intent, whereas 搞亂 have no such implication.

攪局 means to make the make a mess out of the scenario, but 搞局 is "do the scenario" which doesn't make sense.

So no, they are not interchangeable.