Having a separate checkout button for card payment helps buyers realize they can pay you directly with their card, as some buyers may not be aware they can usually pay with a card on PayPal's checkout site even if they don't have a PayPal account. To get that button, you can add any of the other payment services listed here:

PayPal Payments Pro is a $30/mo upgrade with PayPal, which is probably overkill unless you also need to charge "offline" card payments for in-person/phone/fax/mailorder sales. PayPal Payments Advanced is only a $5/mo upgrade, whereas I think 2Checkout, Stripe and Braintree only have a transaction fee comparable to PayPal's with no additional monthly/setup fees. Braintree is also a PayPal subsidiary, so you could link your Braintree and PayPal accounts if you wish.

So if I upgrade to PayPal Advanced for $5 I can begin to include "Pay with Credit Card" in addition to having "Pay with PayPal" button?

Correct, and the separate card checkout button will appear in your cart automatically when you enable PayPal Payments Advanced in your E-junkie Profile.

There is another button that comes with PayPal Advanced and that's "Pay Using PayPal Credit". Is there a way to remove that option from the cart?

PayPal requires us to show that option when the buyer's payment total is $99 or more, so there's no way to hide it; however, it doesn't affect you, as PayPal handles the financing at their end. Buyers who choose PayPal Credit would appear the same as regular PayPal checkouts from your perspective.

Both buttons will show up, no need to link Stripe with PayPal.