Since you are in Ontario, you have to factor in three things that people in warmer climates don't: salt, high insurance, and that 40-minute highway commute. On your total income of roughly 75k, you should realistically look at the 18,000 to 23,000 CAD range. This keeps your payments and insurance manageable and ensures the bartending money stays as savings rather than being eaten by a car note.

The Mazda3 (2016-2018) is your winner here. The manual gearbox in these is one of the best in its class, maintenance is affordable, and it handles surprisingly well. It is the perfect highway commuter that won't bankrupt you on gas or insurance. The Lexus IS is a fantastic car, but if you want AWD for Ontario winters, you lose the manual transmission. If you find a rare manual RWD IS250, you will struggle in the snow and pay a premium for 91 octane gas. Definitely avoid a WRX as your first car for a long daily commute. Insurance in Ontario for a young owner with a WRX is astronomical, and you will be paying for premium gas and more frequent, expensive maintenance.

Regarding your specific questions, you should get a mechanic to look at every single car you are serious about. Spend the 150 bucks for a Pre-Purchase Inspection (PPI) before you sign anything. If the seller refuses to let you take it to a shop, walk away immediately. For a Mazda or Lexus, try to stay under 150,000km. Once you hit 180,000km, you are entering the major maintenance zone where things like suspension, alternators, and cooling systems start to fail regardless of care. Also, in Ontario, kilometers matter less than rust-proofing. A 100k car that was never oil sprayed can be a total loss, while a 200k car that was sprayed every year will be solid. Look at the subframe and the bottom of the doors.