Certainly a dizzying video. The sound is difficult to guess at: I don't know what yours should sound like, and don't trust the microphone much. It just sounds like a motor running, to me.
Your cam chain question does not make sense. What does "adjusted the nut a little bit beyond resistance" refer to, it doesn't describe any part of any 400F cam chain adjustment procedure I know of. The usual issue with cam chain adjustment is that the procedure in the manual does not work (it really doesn't). The original adjuster springs are now all old and weak. You can try a non-running adjustment which might work if the horseshoe is free and the springs have enough push left. You can reliably get a decent adjustment by "helping" the springs via a tool pressing on the top of the plunger rod, through the hole above the adjuster locking bolt (capped with a 6mm bolt). This is done with the engine running: you press the rod down until the chain just goes quiet, and then tighten the locking bolt.
Loud knocking can be a bad thing like loose pistons or worn bearings... but could also be an exhaust or head gasket leak. Worn plain bearings that knock will get worse very quickly until the sound is tremendous and the shocks can be felt through the pegs, seat, and bars... soon the engine starts throwing pieces through its case if you don't stop. A loose piston (worn cylinder and/or piston) is less dramatic and just makes noise, loses power, and burns oil until you fix it. Loose tappets make quite a clacking sound but they are easy to fix: I suggest checking the clearances first.
