I don’t think it is possible to check for file size before uploading it to Adalo db
upload of large-sized files may not work well due to timeouts (I don’t have detailed info how this work from technical side, but it seems there are some timeouts for upload process)
to avoid keeping media files in Adalo storage, you can move them to AWS S3 (for example). The logic will be something like: upload file to Adalo → run Custom Action calling Integromat scenario → in this scenario move the file to S3.
I remember that @JL_LJ had made a tutorial on that, but I can’t find it at the moment.