dont know about your other issues but if you click the speed guage looking thing in the corner of your drives on the main page you can switch from number or reads and writes to speed of them. this will help find drive bottle necks.
Unraid is slow because of the mutliple reads writes it has to do when your moving data this is the price you pay for being able to put any size drive in at any time. you can speed this up abit by enabling turbo write this limits the number of drives used to do this.
Im sure alot of the gripes you have, have a plugin made to handle it. as far as your booting issues that is what the safemode with and without plugins is for.