Can I study both Nat5 and Scottish higher in S5?

As long as u study Higher maths and English +3 others in S5 you'll be competitive for every school in the country. Most uni's recognise that some schools skip Nat 5's and do Highers. Nat 5's are just a stepping stone into Highers so aren't necessary for uni entry. Just make sure u understand the Nat 5 content before moving onto the higher content.

Thanks for replying, though do I have to submit other grades to the uni to replace Nat5’s grades?

no, you'd just have to submit ur higher grades. and the Advanced Highers you do next year.

no, you'd just have to submit ur higher grades. and the Advanced Highers you do next year.

sorry to disturb you again， i wanna ask: without N5 grades and any grades that can replace it can I apply jobs after I graduated from uni?