Like will not be possible - not like with the LTR. If you are lucky, though, it might be possible to apply at one of Thailand neighboring countries. Not known yet. Maybe only possible at your country of residence.
I don't think it will be possible to change to that visa in Thailand. Does not look like it right now - unlike with the LTR. If you are lucky, you just need to leave to a neighboring country - but maybe even to your home country to get the DTV.
It could not be more clear. It is a 5 year visa. It is a 5 year multiple entry visa. With every entry during those 5 years of the visa validity, you can stay up to 180 days each. You can repeat that as often as you like until the end of the 5 year validity. You only need to pay additionally, if you don’t want to leave and extend ONCE more while in Thailand.
It is great for many people. Just be sure you meet the requirements - as in 500k in savings. And be aware you can only apply for the DTV outside of Thailand. If in your home country only or in any foreign country is not clear yet.