the visa has nothing to do with taxation. The two are separate issues and you need to deal with the taxation issue separately - the situation from a tax perspective is the same either way.
it is not just about the bank deposit. Firstly, if you apply from your own country, it not an O it is an OA visa. So, as you say, an OA avoids the need for a Thank bank account balance, but brings with it the need for medical health insurance with a Thai insurer (from a list).
If you want an O then you can apply from within Thailand and it avoids the need for medical insurance, but as you say it does require the Thai bank account and min balance of 800k (the easiest way around this issue is to pay an agent who will then sort out both the account and the min balance)
First, if you spend more than 180d/6 months here you become a Thai tax resident and subject to Thai taxes. That much is certfain.
The issues re what the US/Thai tax treaty does to protect you, the amount of Thai tax you may become liable to, and the allowances (in the tax Treaty and the Thai Tax system) that you can claim to offset any liability, are all questions for a licensed professional. There are any number of accountancy and tax advisors advertising on here and in YouTube to let you contact them and chose which one you like.
The one thing I should add is that currently, the Thais base your taxable income from overseas as that amount you remit (transfer) into Thailand. There are discussions re amending this and start looking at factors like worldwide income not just remittences to Thailand, and also looking at use of foreign cards here to get cash from ATMs or simply paying for items with your foreign card. But all of that is simply discussion. For the time being, it is simply about remittences into Thailand.
i have already read articles from previous sessions with government officials where they clarified that the bank account statements can be from either your home country or Thailand.
not my understanding. Where have you got that from ? It is certainly not in the announcement or anything else issued that I have seen. They simply say you can do a 180d extension per year (so in total can stay for 360 days in a year), so it has been assumed as they do not refer to any new extension fee, that it is the same as all extensions at the moment - 1900 baht.