Do I approach the journal editor before submitting my manuscript?
If you have a concrete and simple question then it could be reasonable to ask the editor in advance, for example "Would a mathematical model of the popularity of film sequels be appropriate for your journal", assuming that the answer wasn't obvious. There is no reason to "check in", and it's an imposition on the editor to pester him/her with merely "checking in". Write the paper, make sure it matches the requirements of the journal, and submit it.