Hi harshalrode,
I can answer based on my own experience, but individual situations can vary.
I don't belong to the 1st group. However, I have heard from some people in specialized IT/telecom fields that they received a job offer. From what I gather and based on assumptions I guess companies with high shortage of skill in Canada would provide offers. To cut long story short the employer has to do lot of paper work and costs to prove they have a serious shortage of that skill - which practically means this is a very small %age.
Coming to question 2, I landed with a PR and did a lot of preparations in terms of bridge training, interviewing techniques, etc. I decided to take some odd jobs including working for a coffee shop. But prior to that I did some networking in my field, had a mentor, did some volunteering, etc. These activities helped me to meet people, understand the culture and get inputs from experienced people to appreciate the cultural aspects and know how to fine-tune myself to get hired.
The sources can be multiple - ranging from online job websites to local newspaper ads to classifieds (Kijiji, etc.). The key thing to note is your ability to customize your resume and offer yourself as the right candidate/fit for a given role. Essentially, for every application or job you customize your resume as well as your cover letter. This is too much of hard work but pays well - and if you wanna simplify it make 4-5 formats for different roles thereby saving time and energy. In many cases if you are overqualified you will not even get the initial interview, so getting hired is a remote possibility. So at times you need to right-size your experience and project yourself as a keen learner and good resource to bank upon.
The biggest dilemma faced by new immigrants is "How soon you want to take up and job" or "Would you settle for a lower level/role compared to what you did in the past?". The answer to these questions depends on your personal situation, financial condition, etc. In my case I decided to go for a survival job as my savings were depleting, but later by God's grace and good timing I moved on to an accounting role with a property management firm. If your financial situation does not permit you to stay without a job for another 6 months you have to plan and make a pragmatic decision - go for a slightly lower role or a survival job for 2 reasons - 1) you cannot drag on doing job search - your bank balance is going down already & 2) Try getting a survival job (retail store, coffee shop, electronic store, etc). Survival job is not good as a long-term career option but it gives you two advantages 1) Canadian experience although its not in your field and 2) some money and exposure to people, culture, contacts, industry developments, general knowledge, language/communication skills, etc. Once you get going you need to schedule your time smartly to keep buffer days for interviews/job search/networking so that one day you can make the right switch.
I hope I've given you the real picture and the right inputs.
Wish you all the best.