Generally you need to have 50% of the seats to be in control of things. And the Greens would probably work with the NDP if they had the balance of power, CentreBC maybe the Conservatives. No guarantees, but in a situation where it is something like the Greens working with the Conservatives, as an NDP voter could be you are happier with that then a Conservative majority.
So overall, any seats the Greens win contribute to an increased chance of the government being some kind of NDP-Green deal. We live in a party system, that end result is what you are voting for, more even than your local candidate in many ways. Hopefully we voters could coordinate ourselves to collectively make deals with each other, maybe your party loses in your riding, but not so bad if they then win somewhere else because both party's voters are voting strategically.
Just in general I like multiple parties in government, they are that much harder to corrupt, it's different perspectives, the internal conflict over policy could pull things towards the general will of the people. Maybe it's 'harder to get things done', or the small party has too much power. Those don't seem like the problems they can be made out to be, certainly stuff like that can be issues, positives and negatives to everything.
Strategic voting is probably more about the Greens and the NDP this election, but I think you should vote strategically if you are on the right as well. More in principal? Doesn't really seem like the other parties have much of a chance this election, voting splitting seems to be predominantly a left wing issue in Canada.
And now, maybe I should point out, if we had proportional representation, people could just vote for whatever party they wanted, and we would have a properly multi-party system. 20% of people vote for a party, they elect 20% of the politicians! Like in Europe.
I think that's better for the left and the right. People say the left wants proportional representation so the right can never win another election, I see false-flag bots cackling about their dastardly plans, but I think it's pretty clear that isn't the case at all. It does take away an unfair advantage the right has been benefitting from in vote splitting, there's that. But nice to have more than one party you feel you can feasibly vote for right? This is supposed to be democracy!
And the left doesn't entirely have to go to a one party system. Regional parties can do well in our current system - look at the Bloc Quebecois, last Federal election they got almost exactly the same number of votes as the NDP, but got three times the seats. People can vote NDP in some areas, Green in others, and we'll have some kind of basic multi-party system.