Do you still apply even if you were given a job offer?

I got an email today asking me to send my application via their company website (i applied through job boards muna kasi). I recently got a jo na though sa iba and i plan to take it naman talaga. should i still fill out yung sa company website kahit na sure na ako sa isang company? would that have any consequences sa company na nagreach out if i decline na lang sa initial or something?