What latex template to use when you do not know the journal you are going to submit
Duplicate of this question on TeX stacckexhange

https://tex.stackexchange.com/questions/514898/how-can-i-format-a-document-for-submission-to-analysis-journal/514906 

My answer: 

If the journal doesn't give you style files I suggest just vanilla arrticle class. If the paper is accepted they will format it. If not, you haven't cluttered it with formatting some other journal won't like.