To manual trim or machine trim

You need to add lock stitches and trims in whatever software you are using to create the lettering.

with that many i would consider using a mesh fusable backing after you cut the backing away so it doesn't scratch the skin.

I run a multi-head and prefer to have my machine trim for me.
I only manually trim during garment finishing, where necessary, a stray end or something like that, prior to bagging and packing.

The way I see it, why trim manually when your machine will do the heavy lifting for you.

Also, if you plan to trim between letters, machine or manual, make sure that a lock stitch is in place at the trim point to stop design from coming apart at that point.

it is cleaner too to have a machine trim after each letter.

If you double click the lettering the properties tab opens up click on tie in and off on the left. Choose "always" on when to tie. Check tie in and tie off n click apply.