Freeing the timber from pallets is hard enough without trying to size and acuratly cut the same time.
Step 1. Use a cheap jigsaw to attack the pallet.
Step 2. Use a tri square and mark all around individual planks.
Step 3. Use a standard Tenon saw to cut to size. Use the bench hook you made earlier. And saw slowly while your skill for cutting straight edges slowly becomes second nature.
If you have a lot of wood to cut a basic mitre saw is godsend and easy to use. While they are essential for long cuts, personally I find hand held circuler saws a faff to use and you need a invest in a decent one.