Please tell where you don't need for example 800k in a Thai bank if you change from tourist visa to a 90 days Non-O based on retirement. Isn't that a financial requirement?
The "Purchase property" reason also triggers the transfer to show up as international/foreign together with "Funds for long term stay in Thailand". If it shows up as international or not depends on the receiving bank. Same with the bank code.
It's for every 1 year extension. It's done in a few minutes as long as your documents are in order. At Chonburi immigration in Jomtien, you can pick up your passport next day. Thats the only difference.