1) Why on earth do you have to strip a stair and a banister? All of those balusters? Yipes! Short of restoring some antique woodwork, I can't think of any reason you would need/want to do that. Are you sure you want/need to strip this? It will be a heinous job.
2) There is no best chemical paint remover. What works for latex may not work for oil, what works for your 6 year old doors may not work for your 50 year old trim, what worked yesterday may be reformulated and not work today. If you know specifically the type and age of paint/coatings to be removed, it might help with suggesting a remover. Or, if you don't know, that's a fair answer too...some are better strippers for "unknowns" than others.
3) You are really in for a messy, messy, painstaking job, that may require multiple strips of different chemicals that will stink the house up for weeks and provide you with lots of hazardous waste to be disposed of, and may still need a huge amount of mechanical removal (sanding)....are you sure you want to strip this?