What are the best long-term visa options for a Canadian citizen over 50 wishing to stay in Thailand?

Hello all, I would like to get your help in order to decide what should be my next steps.

I am a Canadian citizen (normally visa exempt).

I am currently in Canada.

I am looking at the at the best strategy to get in Thailand for long term stay.

I am over 50 and have financial means but I do not want to go Elite visa.

I already have a non-resident bank account with Krungsri and can easily transfer 800,000 THB.

I understand that whatever I do, I will have to to undergo a 14-day quarantine at a hospital or certified alternative state quarantine (ASQ) hotel upon my arrival.

My question(s):

1- Should I simply ask for the special tourist visa (STV) that allows foreign visitors to stay in the country for 90 days, extendable up to 270 days and see from there?

2- Should I ask for a Non-Immigrant Visa, O-X 10 Years Long Stay ? (What is the difference, advantages and inconvenients compared to Non-Immigrant Visa, O-A ???

3- Should I look for a job, an get in as a Software Engineer under a Non-Immigrant Visa Category EX

4- Once inside Thailand, is it possible to convert a visa into another? If I enter under a retirement visa, can I find a job and obtain a work visa (without exiting the country). Or in reverse, could I enter under STV and ask for retirement visa or a work visa?

Thanks in advance.