Is this a real email from jagex or phishing link? How can I tell

It's obviously a phishing email.

It said I received an infraction for RWT

They will never inform you about this through email. You will notice it when you attempt to log in or see a message in your message centre.

But I was curious and clicked the link they gave me to view evidence.

Even if Jagex would send an email about this, they will never send a direct link. They will give you instructions to look in message centre.

Could the link have installed anything without my knowing?

The realistic answer is no.

However, they will log any information you've entered. So change it as soon as possible. I would also recommend to change the registered email.

/r/2007scape Thread