Hearthpwn

Why Beardo in a deck that already has this effect with tavish?

I piloted a similar deck to early legend so I'll take the liberty to answer you... Beardo comes online much earlier than Tavish as you basically only need to complete Step II of the questline (hero power to 0 mana) plus Beardo himself costs two less mana than Tavish.
I'd go as far as saying that if you're on the coin and/or you know you're up against a Reno deck, you want to keep Beardo in the mulligan.

Similar to CaptainJaeger above, it gets you rolling on the Zero Hero Power Train a bit earlier. I have a replay where I had a pretty terrible mulligan and then a few misplays (difficult to get solid games with a 2.5 year old potty training in the house), but turn 6 is a excellent highlight of why Beardo is a great card: I would burn my whole turn getting Tavish down, when I was dead to rights at 1 hp. He allowed me to heropower, draw into him, and then spell/HP/spell/HP to a win I had no business securing otherwise. In a meta where turn 6 is "end game" this was the deciding factor.

https://hsreplay.net/replay/NDXvX4J24NKpoeYCAVBMXZ

Show show, I've seen the idea. Crafting right now.

I love screenshots like this. No statistics, nothing. Just random deck name with current rank in wild. 

sorry, i forgot to screenshot during the match, but there is no point to do as you said. This is a strong cancer deck anyway

Does Beardo give you two hero powers after every spell in combination with the final quest reward, or is it more of just an extra early game tool?

Good solid cancer deck. But I would remove Resizing Pouch and 1x Coldlight Oracle for the very important Secret Plan.

Hearthstone Wild 2021... when late game means you've survived turn 6...

Indeed, I played this deck the first day expansion release but now I hate it so much