Having any amount of available credit to spend on your credit card shouldn't affect your credit score if you use the available credit responsibly and pay back the balance that you use on time.
When using a credit card you should only use the amount from the available credit that you can pay off in full if you want to have a good credit score.
Having too many credit card accounts open can harm your credit score as well as applying for too many credit cards or loans in a short amount of time.
Every time you apply for a new credit card or loan they'll place a hard inquiry on your credit report which can lower your credit score. So only apply for new credit cards or loans if you absolutely need to.