2. Agreed with getting cash from ATM. Just make sure you choose to withdraw local currency and don't let the machine convert your withdrawal to USD. I have Chase (Private Client which is easy to get now) and Fidelity which both reimburse ATM fees.
4. If you have an iphone with esims thne get Airalo. I have used it several times in Japan, Taiwan and Ho chi Minh, and it is awesome. It is 4G and you can get local or Asia for 7 days or more. If you run out of data just add to it. The company is based in Singapore.