I'm kind of making a database using the google sheets query function, and i'd like to know is there a max amount of IMPORTRANGE I can do in a query or is there a max amount of cells that the IMPORTRANGEs are drawing on to perform the query. I'm returning a max of maybe 15 rows, I'm using it as more of a search feature.
There use to be a limit of 50 IMPORTRANGE functions in a spreasheet but it was removed. Now you could have as many IMPORTRANGE as the spreadsheet + your connection + your device are able to handle them.
Bear in mind that sometimes the cells having a IMPORTRANGE function shows Loading... instead of the imported values because the import task was taking too long. Sometimes this is solved by refreshing the web browser tab where you have opened the spreadsheet.
Regarding a limit of the number of cells, there is one. For details please How to work around the IMPORTRANGE error: "Results too large"?