Hard Pads!!

You can slam really hard in aggressive and knees are often the second thing to hit the ground. If you have knee pads, some of the safest ways to fall are onto your knees. I find a hard knee pads have enough bulk that they protect the side of my knee even though there isn't that much padding there. If it is an issue, do both!
Ideally you want something that isn't going to move around on your leg when you fall. I really like Ennui's park pads as the sleeve and the rubbery bit at the top and bottom keep it in place really well.
https://www.amazon.com/Ennui-Park-Knee-Gasket-Protective/dp/B07QQF4881

Also, soft pads will probably get shredded pretty fast if you actually fall on them.