Soft breaking hurts the stronger player
I play run-out 8-ball when I'm in stroke, and everyone in my league that I would call a "much weaker player" does not. Instead, the "much weaker players" rely on strategy, blocked pockets, and tied up balls to be able to give themselves a chance against a stronger player. If I were to soft break, that would nullify my advantage and play straight into their strengths.
So against a very weak player, on my break I bust the balls open as hard as I can, usually make one or two, and then attack my problem balls to get them out into the open. Sometimes I can break them out just right, and run out the rack. Other times when I miss (since I just don't break and run out all the time, sad as that makes me), the SL4 will consistently either dog a ball or fail to execute a safety, and I'm out. It's the exact opposite of what you'd want to do against a good player, but against a much weaker player, I win almost 100% of my racks of 8-ball.
The times I lose are when the balls are tied up enough that I can't get mine free during the course of the run, and it ends up coming down to just a few balls on the table. At that point, I will consistently either go for a break-out and mess it up so I have opened the balls up but I can't get out, or I will go for a safety which is very difficult due to the small number of balls on the table and miss by an inch and sell out.
So break really hard and get a good start on the runout, including the part where you move your balls that need moving. At that point, you win if you don't miss, and against a weak player, you also win if you do miss.
-Andrew