Video size limit is 75mb, as Manton stated in his prior response to you, noting that it used to be 45mb and that may be in some spots that you can report as out of date.
I have no knowledge if/what the image limits are, but images are always processed when uploading to Micro.blog (a lot of metadata is stripped, including some important information like color spaces).
By default, I think the Micro.blog app resizes everything to 600x600.