For the machete/knife discrepancy, based on when I poked into it (superficially, I may be entirely wrong) and looked into mods that (usually over-)buffed the machete when I was doing AGI build in 1.4: it's something to do with the damage type. I'm not doing an AGI build now so I'm not able to test, but (and I may be wrong) I just poked into the items.xml and did a couple quick-and-dirty searches to confirm what I remembered:
"Damage_type" values:
Bone knife, hunting knife use 'Piercing'
Machete, stun baton use 'Slashing'
Wooden club/bat/steel club do not have a damage_type
Stone, iron, steel sledgehammers do not have a damage_type
Basic and iron knuckles use 'Bashing', Steel does not have a damage_type
Now, the damage_type values are listed under the action0 and action1 groups, which I assume to be primary/power attack. Again, I don't know code, I just snoop; again, I speak with minimal confidence on the matter, this is just my poking over time. When I changed machete's damage_type to piercing in 1.4, I got knockdowns with it.
What might also be a factor is the weapon "Tags" values. Clubs have no damage_type on their action0/action1, but their 'Tags' call out both 'blunt' and 'club', whereas hunting knife only has 'knife' and machete only has 'machete'. Batons don't look like they have any weapon type tag in their "Tags" (Maybe 'light'? I don't know what these tags are used for.) There's also perk/attribute/etc callouts in the tags, but I'm just looking at weapon-related things.
I just figured it was an oversight that developed over time. This is just what I learned before and have now investigated on my own, without much knowledge, just doing searches in the .xml based on what other people had mentioned before.
If we're talking my own personal opinions, then knives should not be able to do knockdowns but machete could; that'd help make the machete feel like an upgrade over the bone/hunting knives, though that might also make them feel worse at their progression tier.