If you wish to submit, I recommend you try the bulk submission since it can save you money. However, you have to be careful to submit according to PMG's steps/guidelines. A Modern World Bulk (X 50 post-1957) submission is different/less expensive than a regular World bulk (X 50 pre-1957) submission. You must ID each note plus give an estimated value (no errors) for each. You cannot mix the two categories (on 1 submission form)! To submit less (or very rare notes), US Large size (or US Modern) then you must use separate forms for each & (if rare) designate which tier the note belongs to so this gets even more expensive (& time consuming).
If you are submitting, I recommend you take your time & consider taking 1-2 weeks to be sure your submission form(s) (P#, etc) match the notes you are submitting exactly in the same order (don't mix the notes!) If you submit a note which doesn't qualify, it won't be graded & will add time to the process (they will send it back). YES: they will only use FedEx & they charge step-by-step. I wish it was less complicated but it is definitely something you must take extra care in assembling/putting together.
I put together a PMG RESULTS page on my Notaphilyc Culture site which you may find as a useful guide. Every collector who submits to a TPG usually considers a minimum $ value (threshold) for each note. If you scroll down to the bottom of my PMG RESULTS page, you'll also find a good Youtube video on how to submit as well.