Hi, I'd like if the following sentences are ok. Thanks.
1. Actors didn't wear period costumes as nowadays
2 Actors didn't wear period costumes like nowadays
3 Actors didn't wear period costumes as they do nowadays.
#1 and 3 are correct. 'Nowadays' is an adverb in both cases, with an elided clause ('they do') in #1.
#2 does not work unless you are instancing costumes with other items: 'Actors didn't wear period costumes like Roman togas or Elizabethen ruffs'.
PS: To be thorough, I should add that you will certainly hear your #2, but it should be avoided in careful writing.