Learn English – Should I use was or were with a two-item list

In Standard English, were is the only form used with you. "You was" is ungrammatical in Standard English.

You must be confused because you must have seen both "I was" and "I were". Now that is a separate story, which has to do with the so called irrealis.

If I/he were a bird, I/he'd fly all day. //irrealis

I/he was a very noisy child when I/he was young. //indicative mood.

However, with we/you/they, "were" is used in both cases

If you were a bird, you'd fly all day.

You were a very noisy child when you were young.

Do note that in certain non-standard dialects, notably the African American Vernacular English, "you was" is possible

Yo, what's poppin'? Tell me why you was so angry with me yesterday.

Lennon was a Beatle. McCartney was a Beatle. Harrison was a Beatle. Starr was a Beatle. Together, the Beatles formed a band called The Beatles.

In my opinion, English doesn't handle this subtlety particularly well, and mostly conflates "the band" with "the constituents of the band". With "The Beatles", the tendency is to refer to the group of members.

"The Beatles was ..." can work, but only in a context where the listener is strongly expecting the name of an abstract entity. It will sound weird if the context can, at all, be construed as referring to the people.