You have 2 BTC.

If I remember correctly, "Bitcoin" was supposed to be the name of the network/project/app and "BTC" the name of the currency unit.

1 Bitcoin
2 Bitcoins

Easy.

1 Euro
2 Euros

Same with all the currencies.

Agree!
Bitcoin or Bitcoins is the same meaning and the value is the same, just different one letter only. I was not really thinking about it but if given a choice, I choose Bitcoins

I would say "two bitcoins" to the OP's question.

On the parallel chat I thought things had settled to:

The Bitcoin protocol.
One bitcoin.
Two bitcoins.

I lol'd so hard at this. But yeah, as others have mentioned, it's up to you, although it seems like it's typically referred to as BitCoins when referred to plurally, at least in America.

in english where is no is only singular and plural. 2 are plural. there are few languages where 2 are nor singular nor plural.

1 Bitcoin
2 Bitcoina
3 or more Bitkoini

English have just
1 Bitcoin
2 or more Bitcoins