This is the advantage of an OA Visa is that you can have the funds anywhere. In particular you'll have a one year Visa which will make it very easy to open a bank account once you get to Thailand and then transfer your funds into your Thai bank account to get the extension for year 3, assuming you did a well timed border bounce just before your Visa expired and your insurance was extended near the end of year one.
Pretty much no, tho some schools operate other activities such as Muay Thai as well. Only choose a language school if they have a verifiable track record of DTV approvals along with which embassy approved their documents