#1 option is out because you cannot train for your your Canadian CDL license unless you have already got legal status in Canada which in your case would be a work permit at the very least.
Also you need to know that since last year the new MELT mandatory training course for class one drivers costs $10,000 and takes a minimum of 6 weeks full time hours.
Prior to that you would need to exchange your UK car license for a Canadian one and then take the airbrake and class one written tests.
You need two forms of Canadian proof of address such as bank account, Canadian SIN number, etc to do that.
#3 option is possible but you must bear in mind that seeking employment while visiting Canada as a tourist is strictly against the terms of your entry so you would need to be careful about it and definitely do not travel with any related paperwork such as a CV. If you were unfortunate enough to get your luggage searched at the airport. You would almost certainly be turned around at that point.
#2 option is the easiest and least risky but to be honest, the current cost of training that I already mentioned is likely to discourage potential employers from considering recruitment from overseas.
If you are young you could think about the yong person’s working holiday visa option although you would need to save up a lot of money to finance it and of course you would also need to find an employer.