I will be using the computer for web browsing, emails, word processing, spread sheets, video and photo editing. No gaming. if that is all you are going to use the machine for then your spec is more than adequate. However you don't mention graphics at all, if you are working with video get a decent graphics card. The number of processor cores will have no effect unless you purchase video handling software that can make use of them. For simple web browsing, emails, word processing a single core is fine - if you have spreadsheets with lots of mathematical calculations then more cores may help. Get the fastest processor you can afford and that is not necessarily the one with most cores.
OnePlus 5T review: Hands-on