It doesn't have any impact on "how universities see you", because they make offers (if they make them) before you decide which is your firm and which is your insurance choice.
Once you get your offers back, assuming you have at least two offers, then you pick which of those offers you'd like the best. That's your firm choice. If you achieve that grades specified as part of that offers (the conditions), then that's where you end up.
However, you can (and normal would) select a second choice to be your "backup" or "insurance" choice. If you don't meet the conditions of your firm choice, but you do meet the conditions of your insurance choice, then that's where you end up.
It's normally the case that the insurance choice would have lower grade requirements than the firm choice.
Just to muddy the waters slightly, even if you miss the grade requirements of your firm choice, they might opt to accept you anyway.
If you don't meet the conditions of either offer (and neither decide to accept you), then you can try finding a place via UCAS Clearing (where students without places are matches with courses with availability).