That middle tip is good for general purpose use. It should have enough heat mass and still be sharp enough and flat enough too.I am getting the TS80 soldering iron which is said to be quite good, (probably OTT for me but I need something I can use with a battery pack.)
How do I know what temperature to use? My iron has a chisel tip like the one in the middle of this picture
, I was thinking of getting a conical tip (the TS-B02) for it but the TS80 tips are like £15-20 each!
I would prefer to save that money if you think the chisel tip is good enough.
For heat some people like to use the readout for temperature control. Some irons do not have accurate control so use the heat control and use your senses too. I like to smell the flux and see the smoke and test the solder flow when melting it. If the flux goes up in smoke too fast the heat is too high. If the solder burns and becomes mottled and not shiny it's either too hot or you did not allow the solder to cool before moving the item. You should be able to see a small drop of melted solder on the tip while holding the iron. Too hot and the solder will run right off and too cold and it just doesn't melt properly. Experiment on a old circuit board and you'll rapidly get the feel of it. If you can find a old through hole PCB and a PC motherboard you'll have lotsa stuff to practice on and perfect your technique and skills. Have fun!