For lower elos, it comes down to an "It Depends" for all four of those. You can't expect one champion to win a game alone in Lol anymore - it's not like it was in past years, when people were bragging about how one player was able to carry a whole team.
This is especially true when you consider that Silver IV-V is roughly the half-way mark for the entire League population - i.e., the "average" rating of the entire population. (At season 6, you have roughly 1/2 of the playing population is in bronze, believe it or not.) So, plan to play a solid champion - and if the window opens up for one of your favourites, because it works well against the team across from you - then go for it. Incidentally, I've seen an Akali and an Orianna doing fine in lower ranked games.
The only thing I'd suggest is to just stop worrying about the end result for a while. Simply, it's not healthy. If it really bothers you, then play some normals or ARAMs for a bit. Fretting about outcomes at lower levels really is not worth it. Just focus on your game and improving the basics. Eventually, statistically, you will gradually get out of the lower levels and get a chance to play some of the champions you want. But worrying really does nothing for you...
because in bronze/silver a good team is so rare, and these champions just cant really carry as hard as say rengar for example
