The tool I use is actually quite expensive
I don't use the dimple part for insulated/heat shrink fittings though, rather (as the tool itself suggests) I use the flat part (looks like two sections of a circle, deeper into the tool). As far as size goes, tool is sized for wire 16 and up - so it isn't universal but I really don't have many smaller fittings on the boat, and I do own a standard (also non-dimple) crimper for those.
I haven't cut the fittings though it may be interesting to see, but I do know that they are crimped flat. I might sacrifice one this weekend to see what it looks like inside.