I didn't need the pick. After unscrewing the ten screws, it was easy to lift off the cover from the back grills with just slight leverage all around with fingers to open the rest. I also didn't need a tool to access the RAM compartment.
I'm not the video author but I can answer that. You can always open yours up to see what will fit; I think you can fit two 2280s. Mine looks just like the one shown and I could expand mine with another 2280. (Lenovo Legion Slim 5 16APH8 is the exact model I have.)
I read a forum post that said that the 2nd slot will only take a single sided SSD such as Samsung 990 Pro 4TB which is what I'm going for. If you're going large capacity like 4TB, I suggest you check this and stay with single sided. For example don't go for WD Black SN850X 4TB which is double sided and may not fit. YMMV.