One of the biggest mistakes I made writing the early drafts of Guns and Guano was being vague. When I started out I wasn’t confident in getting an American protagonist right, so I fudged his accent and was vague about his background. But such evasion is not getting it right, as became clear the minute I got the book near beta readers. Specificity is what makes characters real, because real people and places are specific and detailed.
You can write something in a vague way from the start and then fix it later. But if you’re doing that then why not write something specific, which you might stick to later? You’ll be no worse off. Pick a name for that random bodyguard, decide which town the action happens in, know which side of the war your character fought on (yes I tried to fudge that, no it did not work). Even with accents, pick one, do a few minutes’ research and then go with it. You’ll still be doing better than my original cowboy-impressionist generic American.
Better to take a risk on a detail and maybe get it right than to be vague and be sure of going wrong.