Oakeshott typology is the way to divide existing medieval blades based on their general shape, dimensions, properties.
It generally can be applied to the swords from ~ 1000 - 1500 period.
It's very popular, and while ancient people didn't really care about any divisions like that so much, it still allows to categorize sword based on their overall function pretty neatly.
Link
He is quick, neat presentation.
Here some description
To best of my knowledge "claymore" is more modern english version of gaelic word that was used to describe traditional scottish swords.
Baskethills like that actually, not two handed swords.
Later, it began to be also used to describe two handed (claidheamh da laimh), mostly cut oriented swords with characteristic guard - sloping towards blade, with characteristic quatrefoil ending.
And it's pretty much it -
here is page about reproduction of early two handed claymore, with nice explanation of what they were - pretty classic XIIIa blades mounted in characteristic fashion.
So while Wallace could theoretically have longsword, looking like that, he could have claymore. But since all signs on heaven and earth indicate that such style developed much later, he most certainly would just longsword like many other longswords in 14th century.