Ok, so here's the deal: I live in Brazil, the Country of Residence in my Wii U was set as Brazil, I created a Nintendo ID, everything Brazil. Then I tried accessing the eShop. Wasn't available in my country. So here's what I did: set my wii u to Canada, created a Nintendo ID set as Canada, everything Canada. Then I tried accessing the eShop. It worked! So I downloaded some demos (which was the sole purpose of creating the Canadian account), ok, cool, everything is pink.
But then I realized I had to keep switching back and forth between Brazil and Canada to play+miiverse/eshopping respectively. So now I'm in doubt whether to play using a canadian account (which would not be a problem, since I'm okay with starting miiverse and NSMBU all over again) or to keep playing with a brazillian account (I would create a third account set as canadian, but that's okay, really).
Are there any advantages/disadvantages to doing this? Will there be any difference if I play with my wii u set for Canada instead of Brazil? I don't know why I'm so scared of doing this, since apparently the only difference is that I won't have to go to settings every now and then if I do create a canadian account and play as it.
WHAT SHOULD I DO???

Since there isn't any option to use the eShop in your country, I'd use the Canadian setup. Shouldn't you be able to set the Wii U language to brazilian portoguese even if you use the Canadian setup?

I am able to do so. Not that I do it anyway... It's in English actually haha

my main question is "will there be any differences during online playing (mainly smash bros u and mk8) if I set it up as canada?"

Only what it considers as "other players from your region"

I remember that whenever I played regional Mario Kart Wii online races it would connect to the whole America, not only South America.
Well, thank you, I'm gonna do it.