If you have full edit privileges, anything that's a clear improvement is fine, even if it's small. Please feel free to fix small errors, especially in newer posts or prominent old ones.
But one thing to be cautious about: make sure you try to fix everything there is to be fixed. It's unfortunately common to see edits that fix a glaring mistake in the title without fixing several smaller mistakes in the body. Ideally having enough reputation to have full edit privileges means that you can be trusted to do this! (Sure, if you only have 15 seconds and there's a glaring error in the title, it's still good to fix it, but it's far better to look over the whole post.)
That caution applies even more for others who are just suggesting edits. If you suggest one fix and leave several other mistakes, you're basically forcing the reviewers to do the work that you didn't. At that point, reviewers might choose to use the "reject and edit" option, so that they can fix everything and mark the suggestion as not helpful, and probably should do so if it's a consistent pattern.
If you're suggesting edits in good faith, please don't worry, this will never happen to you; it's totally fine to miss things here and there. I mention this only because the main answer here is endorsing minor edits, and I don't want to see it used as a justification for low-quality suggested edits.