Are Amiibos required for SSB:U?

I haven't owned a Nintendo console since the GameCube and therefore haven't played SSB since SSB:M so I'm not familiar with how this works.

I'm planning my holiday game budget and wanted to know more about SSB:U (I don't want to get this game if it's P2W). I see a lot of people online excited about SSB Amiibos, but I haven't been able to figure out how they're used in the SSB games.

The Nintendo website makes it seem like they're some kind of P2W mechanic (from how I understand it, you get some kind of OP sidekick when you scan an Amiibo, giving you an advantage over other players).

From Nintendo's description of Amiibo functionality in SSB:Wii U

Customize your amiibo™ figure as the ultimate sidekick, and level it up to CRUSH your opponents.

https://www.nintendo.com/amiibo/games/detail/HPp-wrUaZHOKvK_GzCJ9eDkIom6x_TEA

Now, can you use these in normal online play, or just some kind of mini-game mode? I know Nintendo pushes Amiibos hard in some games, tying key DLC to them (like in BOTW), so I'm trying to figure out if SSB is like that.

TLDR: Will I be at a disadvantage in SSB:U if I don't buy Amiibos?

No microtransactions. And Amiibo's are not required for anything.

So you can train an amiibo as an AI fighter, but apparently they can also unlock the character of the amiibo.

You can still unlock regularly in the game and the first feature is honestly just a "oh that's cool" type of thing, so no, they are not necessary.

@sonic_spark: Good to know. I wouldn’t want to get into the habit of collecting Amiibo. Lol

amiibos are just extra content that you can waste time on.

nothing essential.