What do you mean by leverage? A alot of people throw that word around, but I have never understood it's real meaning, as a foreign speaker.
Based on the the little jujitsu I have done, strength and endurance is more crucial than speed.
Leverage
"Leverage" is sometimes used literally. For example when we do an armbar, I think the reason we grab at the wrist instead of at the forearm is because it is literally the furthest, stable point along the lever of their arm.
Same for a tripod sweep - we grab at the ankle and push at the hip because they are the furthest points along the lever of their leg. I think grabbing further on the lever may minimize the necessary amount of input force on one side of the lever to produce the same output force on the other side of the lever.
At other times I've seen instructors use this word to mean using relatively strong parts of your body to control, isolate, or damage relatively weak parts of their body; basically, putting your opponent out of position to respond efficiently. For example, your arms are relatively weak but they can be an efficient, offensive option if your opponent can't use his arms to defend a RNC or anaconda. I'm sure leverage in the literal sense is at play in these scenarios as well, just in more nuanced ways than I can comprehend.
There's a dude named Doctor_Kickass on IG who I believe is a Ph.D in physiotherapy and a Dynamix black belt. He is always releasing insightful content on fight biomechanics - mostly grappling related but some other stuff too, like concussions.
Attributes
Personally, I would agree with on endurance and strength being more important, but purely from a technical standpoint. What I mean is I think endurance is important because it allows me to be on the mats longer. Furthermore, being stronger will make my body more resistant to injury and also allow me to stay on the mats longer. More time on the mats means I have more opportunities for technical improvement. Strength and endurance offer direct benefits in regards to defeating opponents too but it's just a nice perk. While it's not a stretch for me to imagine that speed also elongates my mat time, it's more abstract for me to imagine how one correlates to the other.
I think these attributes will give a huge advantage competitively, however, particularly in weight classes which stereotypically lack a certain attribute. For example, big people who are strong but also have speed are a nightmare. I think that's why people like Buchecha and Erberth Santos are such outliers.
While a little harder to observe, I'm sure being strong at the lower weight classes where everyone is already fast is also a huge asset.
I've heard before that 170-180lbs is the perfect balance. Big enough to be strong but small enough to be fast.