The arms were probably a lot more complicated than the basic 'de la Pole' ones and were probably quartered with those of his mother, Elizabeth of York (like Richard Duke of York's but labelled for difference), to stress his 'royalty'. His older brother
Edmund's arms would be very similar.
His standard is anyone's guess. I would imagine that as a noble he would have his banner bearing his arms with him, but a standard I'm not so sure. Certainly his personal 'household' attendants might have worn a rose, as generally people were known by their badge... albeit 'White Rose' might just be an everyday reference to his Yorkist antecedents in this case though... if it derives from him himself though, I'd put money on him using it as a badge.
His status is a bit ambiguous and I'm not sure whether he was actually a 'commander' or just along for the ride as a 'gentleman volunteer', if the former he would pretty much be able to choose the standard which his men followed... but what that was, I couldn't say.
Stuart, you've probably read far more on this already than I have, so this is more 'opinion' than based on any sort of research. Seward's 'Last White Rose' is in my 'to read pile' still.