changing product pages in to one item scroll down menu

Is there a way to alter a template/theme if you don't like the layout or features of it. I am having to use a plugin which is a central part of the site and it has to use the journal theme however, it is very slow (in my opinion). Also i wanted to ask, I am selling products by square feet, which are the same and rather then selling 1ft x 1ft then all the way up to 20ft it doesn't look nice on the cart as individual product listings. is it possible to do this as a dropdown which would look alot cleaner and just provide a link to the actual file as opposed to having multiple product listing which are the same and repetitive and looks a little untidy.

Thank you

I suggest you use product options.

Display only 1 product with multiple "size" options.

Is that any good?