I use the same materials to add jumpers to a speaker cable as I do in the main part of the cable. Not doing this will hurt the total performance of the cable. However, jumpers have different design consideration then the main part of the speaker cable. My preference is to use the same number of total circular mils of conductor material for both the main and jumper parts of the cable.
There is nothing like run bi-wire cable to speakers if you have a proper set of speakers and amps for the task. The performance will exceed a speaker cable with jumpers by a considerable margin. Here is a link for more information
HOW CRITICAL ARE JUMPER CABLES
When using jumper cables instead of biwire speaker cables, do the jumpers need to be as good a quality or better than the actual quality of the speaker wires? The jumpers need to be 6” to 9” long. Also is it better to hook the main speaker wires to the low end and then run the jumpers to the high end or visa versa?