With a US passport you’ll still get a 60 days visa exemption and free stamp upon arrival. Nothing is turned back to 30 days. ETA is postponed without further notice but you need to du a TDAC arrival card from 72 hours prior to arrival in Thailand.
Based on several feedbacks and also personal experience it’s not just straightforward to open a bank account on a initial Non O visa anymore. You might have to try several branches as they require a minimum one year "visa".
It’s should be sufficient with three months, you’ll need to update your bank book same day as you apply and bring a so called "standard bank letter" as well.
For a three weeks stay on a 60 days visa exemption there’s no issues to re-enter Thailand and get another visa exemption at the border/airport. You just fill out a new TDAC.
If you really entered Thailand on a 60 days tourist VISA you applied for online as a e-visa and payed around 40 USD before you entered Thailand, you’ll need to purchase a re-entry permit in order to get stamped back in again.
Yes you’ll have to report after 90 consecutive days anyway, you won’t get any trouble at the airport but you might and probably will be fined at the immigration next time you register.
With Italian passports you’ll normally get a 60 days visa exemption and free stamp upon arrival which can be extended with additional 30 days at your local immigration.
Almost impossible to open bank accounts now. You’ll probably have to contact one of the bigger visa agencies in Bangkok who still are able to open and provide this service as a part of a total visa package or apply through an embassy at a nearby destination with your bank at home.