The OP has asked two questions. Quality of life? Working as an English teacher?
Firstly, quality of life is a wide term. It also depends on your priorities and where you live in the city. Some suburbs are isolated, but quiet, other are in the center of things, but noisy. Both areas are good for some, but not for others, depending on preferences.
Health care is easy and cheap, as already mentioned. Eating and drinking out is cheaper here. Weather is moderately good most of the year. The general pace of life is slower than places like Shanghai. Kunming has also gentrified and westernized a lot in the last few years. Traffic sucks, but ebikes and pushbikes are ubiquitous. Petty theft is common, but not as bad as a few years ago, and crimes against the person (violence etc.) especially aimed at strangers, are rare.
Secondly, teaching. Temporary gigs are unusual, but some exist. How good is the work? This has a lot to do with the employer. There are good ones and bad ones, just don't expect the employment rights that people get in Canada. Some teaching gigs are easy. The English language training mills can be easy as you teach from a book, and there is minimal class prep, you also get to teach the same unit several times and it becomes familiar.
Teaching in the public sector is harder, as you can spend many hours on class prep, especially if they are using an unsuitable book, chosen by someone else years ago and the school/uni won't buy new ones. You then need to create classes from scratch, not easy for a newbie.
If you are a Canadian citizen, you will need to check the requirements for being a foreign English teacher (bachelors degree, 2 years experience, a recognized TEFL/TESOL/CELTA certificate, and criminal background certificate).
I do not know the requirements for a Chinese national English teacher in a training center. However I think the public sector would be closed to you without a relevant teaching degree from a Chinese university.