I know I could split the queries into 2 or 3 and combine them if I only specify 4-5 lookup fields I want to retrieve each time.. But is it possible to get all of the lookup IDs with CSOM in one CAML query as you can via REST (e.g., /items?$select=AuthorId,EditorId,LookupOneId,LookupTwoId,LookupThreeId . . .LookupTwelveId)?
Onprem you can (but shouldn't) increase this per Web Application, but in Office 365 you're limited to 12.
See SharePoint 2010/2013: List view Lookup threshold uncovered for more details.