I have a pair of hemos that have a little scissor section that works great. Or some cheap pliers I picked up at Academy work well too. When I first started using braid, back when it first became a thing, I had some small side cutters that were awesome for cutting it.
I never use a leader and it hasn’t made a difference. Tested that many times on streams that are gin clear.
Never learned any new knots either. The ones I started out using have always worked fine.,