They're simply visual differences for identification.
After Apollo 11, folks on the ground had a hard time finding photos of Armstrong on the moon. Most photos were taken by him and there was no obvious way to distinguish the two suits. After that stripes were added to the commander's suit for the remaining Apollo missions.
As far as I'm aware, the stripes on the current US suits have no specific meaning or designation. There could be some operational considerations, but I've never seen them mentioned. A broken "candy stripe" is also possible.
From this NASA page:
Some suits are plain white; some have red stripes; and others have
candy cane stripes. These variations help to tell one spacewalker from
That said every astronaut does not always wear unique suits. The press release for an upcoming EVA will usually identify which is worn by which astronaut.
This will be the 196th and 197th spacewalks in support of space
station assembly and maintenance. Kimbrough will be designated
extravehicular crew member 1 (EV 1), wearing the suit bearing red
stripes for both spacewalks, the third and fourth of his career.
Whitson will be making the seventh spacewalk of her career and match
the record of NASA’s Suni Williams, for most spacewalks by a woman.
She will be designated extravehicular crew member 2 (EV 2), wearing
the suit with no stripes for the first spacewalk.
Pesquet, who will be making the first spacewalk of his career, will be
extravehicular crew member 2 for the second spacewalk, also wearing a
suit with no stripes.
I've never seen information on the SAFER numbers. I'd assume it's just to identify the different units, but have no info on it.