yes, you cannot do any upgrade ram or cpu later at all. SSD is possible but will be too troublesome to do and not easy to do. the cost of buying new SSD with bigger capacity that can be used for macbook pro will be super expensive, and it will cost you more than you pay now for the right size of SSD. importantly, the bigger capacity SSD macbook may look expensive, but in real, those third party of external SSD in terms of performance (read/write speed) are totally sky and earth. 512GB is a minmum even for normal users. dun waste time on 256GB or below.
if you are serious video editing user, the insance write/read speed will make a big difference when you work on the project within the 'working space' instead of external storage etc.
16GB is good if you are heavy user again such as video editing, running VMs etc. else 8GB is more than sufficient even for gaming.
upgrading of CPU is totally not a must, even i5 can do well for normal tasks not to mention it is quard-core, for application that can tap on the benefits of multi-core, it will be good. but of course if you have real need of i7 and money is not an issue, by all means you should go for it.
In the event that you need more RAM and CPU, you should just go for 15-inch, it will save the trouble to even think of upgrading processor or RAM, since it is already i7 6-cores and 16GB, more than sufficient for most people.
i am basically 99% photo. but once in a while I do edit up to 100-150mb per photo file size and foresee that i will doing more editing with photos 30-40mb per file.
let say if i insist on the 13-inch, for 2018 ver, with around RM8500 budget (educational store price), which configuration would you recommend? go for the extra storage space?