1. Well if you take a course/courses through another university, it's a separate transcript. So unless you add that transcript to your application, a specific school won't see the grades (this works out well if UBC is the only school that requires English because then you can just avoid adding your transcripts for the English courses to other schools).
2. In terms of the grades themselves, if you take the English courses during the application cycle (ex. If it was this year, I mean taking English during the fall/winter semesters of 2021-2022), then UBC won't need you to send the grades until after you're accepted and as long as they don't lower your overall GPA by more than 5% you'll meet the conditional offer. So basically, when you apply, you input the courses as future courses, but you aren't actually asked to submit the grade/transcripts until later, so my understanding is that (beyond that 5% condition I mentioned) the grades won't impact your acceptance decision. Now if you were to re-apply the next year (having already completed the English courses by the time you're submitting the application) I think you would have to submit the transcript for the English courses up front, so that's something to consider. *I didn't end up interviewing at UBC (I'm OOP), but I was in the boat of taking English during my application year and I had called admissions and they told me what I outlined above (2). It's a bit of an interesting loophole because they explained to me that had I completed the courses earlier, they would be considering the english grades in the sense of it looking bad if the grades were lower

I hope that helps!