It's really hard to predict the waitlist. However, since the BWV are larger than the BCV, my guess is that the BWV waitlist has a better chance of coming through for you. Of course, none of us has a way to know how many members are on the waitlist ahead of you. MS doesn't even know that,
Yes, standard view units are typically more difficult to get than the Pool/Garden units. IMHO, they are usually just a little more difficult to get than the guaranteed Boardwalk view units. Apparently, when you called, there was SV availability and neither of those two nights fit anyone's waitlist.
If it were me, I'd waitlist for all 3 booking categories at the BWV - SV, PV (Boardwalk) and PV (Pool/Garden) as well as all 3 at the BCV (lock off, dedicated w 2Q and dedicated with 1Q & a sleep sofa). I'd waitlist for all the days to become available at once, so there was no chance of having to move back and forth. In this case, if one of the waitlists came through, the others would be automatically canceled. You could cancel the SSR reservation at the same time - or better yet, cancel it after the other reservation were secured (provided you had enough points to do it that way).
If you have enough points to hold the SSR reservation until the other reservation is secured, I'd pick one option (probably the Pool/Garden at BWV because that category has the most units) and waitlist for each day individually. That will give you a better chance of securing the reservation. I wouldn't do it that way if I didn't have the points to hold the SSR reservation until the other was totally completed, because I wouldn't want to chance moving back and forth between resorts during that very busy period. If you do this, keep your banking deadlines in mind.
Good luck - hope your Mom gets to stay in the EPCOT resorts area.