Anonymous participant every embassy is different and we don't have many reports from Yangon. So these are general answers and might not be correct for Yangon.
1) either should be fine. In Laos after you go in to pay they then schedule an interview. I don't know if Yangon will be the same but part of the interview is them asking you to open your banking app to show the balance at that moment.
2) more than they ask for shouldn't be a problem
3) 6 days isn't very long. They might not even look at your application for a while after you pay but they can see when you submitted your application.
Yangon does not accept payment through the e-visa system. Same as both consulates in Laos. Payment must be made in person at the embassy but at Yangon you're required to have an appointment to pay.
you cannot use it in Thailand. You can only use it when entering. And if the embassy finds you went to Thailand they will cancel your application as you're required to remain inside the jurisdiction of the embassy during the entire application process.
What does your lease say? Generally you either get the bill directly from the electric company and pay the government rate, or you pay a rate that's 2-6x the government rate as a way for the owner to make extra money off of you. Either way it should be in the lease.