I wouldn't say you NEED an SSD . I have one , and yes it is a big plus ,. boot time of 25 secs , and fast load of the game , but it wont really effect your gaming . Graphics , CPU and ram will keep that humming along quite nicely . You may be able to shave a few pounds on the PSU , but , like you I prefer a little headroom . As for the case , couldn't say , I think that is all about the looks , as most decent cases come with similar specs . Good luck .
Surface Pro (2017) vs Surface Pro 4