TIFF can be pita if you want to write EXIF data. reasons are described here (jump to "problems/technical" if you don't like to read the whole wiki):
https://en.wikipedia.org/wiki/Exchan...ge_file_format
as for software, i use ACDSee. great software to organize, great software to tag. if you like to try it - they offer a free trial (14 days or so) to test everything you can do with the software. it also offers a bunch of own metatags and a customizable category/keyword system you can add to nearly every file (if the file itself doesn't support metatags at all, ACDSee stores them in a so-called "sidecar" when you embed those tags to your files - just keep in mind that ACDSee doesn't write these things directly when you "tag" them, you need to start the embedding-process manually. at least ACDSee remembers which files need an update).
with ACDSee you can't change (or add) EXIF data in TIFFs, but you can handle the IPTC metadata and all the ACDSee tags without problems.