not always
You can gain considerable power, size and strength working in the 40-70% area moving the weight at maximal speeds. 100% white fiber recruitment and its frigging taxing! This has much the same effect as using loads above 85% - its called CAT training
Today I did 60% 1RM full squats for 3 set of 5 and boy did that kill me, legs were pumped like balloons! Moved fast as possible in the eccentric and concentric phases
All fibers will grow but yeah white fibers grow the fastest and most. But there isn't a strict division in fibers. Fibers will continuously vary from red to white and all shades in between
Move anything at maximal speed and you will recruit white fibers. But red fibers are always recruited first and then higher and higher threshold fibers are recruited until the required force is exerted. So you never need to worry about recruiting red fibers, but white and higher threshold fibers are a problem.
Using heavy weights and lighter weights moved as fast as possible will do that just fine. But there is a learning aspect to be able to recruit high threshold fibers. You can get around this by using shock methods, dropping and catching heavy weights
, depth jumps and plyos for example. ie drop yourself from a height and land in a pushup position, that will recruit a lot of fibers your can't voluntarily recruit
Once you fail in a set, all the recruited high threshold white fibers are exhausted, so it makes little sense to do forced reps - you'll be just stringing the red fibers along and over-taxing your CNS