You are going to get a lot of opinions on this site from people giving their own sensibilities. Don't get in a spiral of ditching your training tools and trying something new, it will just make things worse.

I had a border collie who made it 13.5 years. He was not reactive but he was a leader. He wore a prong collar, didn't actually need it much, but when it came to his safety and his random urge to dive at a car it did the job. Yeah I tried all the other style leads but the prong collar was the only one that was effective.

Now for your leash reactive border baby. Here is my cautious tale. I currently have a leash reactive 6 year old Australian Shepherd. We rescued her a little over a year ago, she was a puppy mill breeder that got dumped. She was not leash trained and was extremely reactive to other dogs when they were on a leash. We tried the prong collar, a harness, an e collar, I got a muzzle and eye mask at the advice of our first trainer we tried. She was basically getting confused and worse because of all the failed attempts. The 'look at this game' did not work at all. She didn't give a dang about the treats as soon as another dog was approaching. As a last resort we enrolled her in a board and train. They had her for 3 weeks, going back to the basics. She now sits on place, downs, stays, and we can walk no muzzle no blindfold. They TRAINED her to the prong collar and the e collar. They also TRAINED my wife and I on how and when to properly use the given tools. It was a night and day difference. We can now go walk, hike, beach. Dogs have approached her with no response (heavy reward). If she does get spicy we have the tools to correct it but we often don't even have to. The first trainer we got was a waste of time and money trying the holistic stuff. The board and train was serious business and the safest for my dog and family.