I may have this wrong but I think the differences between wavebounce and b-reverse is that b-reverse simply changes the direction you to the B move in, keeping your momentum while going backwards (in the air), whereas wavebounces keeps your momentum but changes it to the opposite direction.
For Lucas, try running and then jumping into magnet.
Then, try running, jumping, pressing Down B, and quickly moving the control stick to the bottom left if you're moving to the right, or to the bottom right if you're moving to the left. If done right, you should then change directions with the magnet AND keep moving, so you'll actually go backwards from your original start point. This is a wavebounce.
The inputs should look something like this.
(Dashing to the right)

>

/

> (

+

) > (hold B) >

(Dashing to the left)

>

/

> (

+

) > (hold B) >
B-reversing, however, would ignore the initial down B input in the first place. To B-reverse magnet, simply do this:
(dashing to the right)

>

/

> (

+

)
(Dashing to the left)

>

/

> (

+

)
Notice that you don't press

at all, just

/

. You should notice that with the wavebounce method, you'll move opposite the direction you came, whereas here, you keep moving in the initial direction.
And no, by wavebounce PKF I did not mean DJC PKF. In order to wavebounce PKF, you have to be dashing (I'll use moving to the right only for this example), and then:

/

> (

+

)>very quickly(

)
You need to change the direction of your c-stick very quickly or else you'll just jump forward in a straight line as you PKF. This method allows you to suddenly change the direction your PKF comes out, as well as your direction.
I'll try to upload some gifs of these later, but I hope this helps.
As for Tether cancelling, it's simply pressing the control stick away from the stage after you tether, but before you "reel it up". You will go back to normal fall, and can do any aerial move out of it (including down B).
Up B Ledge techs? I assume you mean where you carry your momentum while using PK Thunder? If so, that's just done by dashing off a platform/edge and up-Bing as you near the edge/side of a platform.