So I have a evga 1070 sc and all I want to do is have it use a custom fan curve and auto start with windows and use that curve I set. But I don't understand what
 
1. The startup toggle
 
on the main screen it shows where you can toggle it on and off. what is this because there also one in general menu?
 
2. Auto
 
I don't understand this toggle at all. Should it be on or off with a manual fan curve? Its the toggle on the main screen that is shaped like a fan.
 
3. Do I need to save the profile as I'm not overclocking? only fan curve.
 
4. Start minimized is off but it always start minimized on start up.

Welcome to the forums.
 
1. 'Start Up' on the main screen applies the current active profile/overclock settings at Windows Startup..The overclock settings (if any) are written to, and load with the NVIDIA Graphics Driver when Windows starts whether Precision is running or not..A custom/preset fan curve will not load though, Precision needs to be running for custom/preset fan curves to be active..However, a manually set/fixed fan speed will load with the driver whether Precision is running or not..'Start With OS' runs Precision when Windows starts..That's the difference between 'Start Up' and 'Start With OS'.
 
2. When the little fan icon below the slider is blue (aqua, whatever), it's on auto and the custom/preset fan speed curve (or the standard/stock curve if no custom/preset is used) will be active..When it's white, it's in manual/fixed mode..Pay attention to that one because it can be easy to inadvertently lock it at a low fixed speed and cause GPU overheating..A low fixed/manual fan speed can be applied when 'Start Up' is selected even though Precision isn't running..Do select 'GPU Temperature' in the 'OSD Settings' and enable 'Play alarm sound when value is out of range' with a 'Maximum Value' of whatever high temperature limit you want, 83C perhaps, I think that's when your card will begin to throttle due to temperature..Again, pay attention to that one because it can be easy to inadvertently lock it in at a low fixed speed and cause GPU overheating even if Precision isn't running..Real Temp is a good utility to have running at all times with the CPU and GPU alarms enabled.  
 
3. As Loveha said above.
 
4. When 'Start With OS' is selected, Precision always auto-starts minimized, by design..When manually started like from a desktop shortcut, it will start minimized only if the option is selected..This setting has no effect when Precision is set to 'Start With OS', it only affects manual starting.
 
If you're familiar at all with older versions of Precision (X15/X16), the same rules apply which most can be viewed by hovering mouse pointer over most settings if 'Tool Tips' are enabled, same with Precision XOC..Tool Tips aren't quite what they used to be though, slightly lacking in Precision XOC.
 
If you're not very familiar with Precision, you can just monkey around with it to see what's what or search/ask here in the forums..If you're not happy with Precision/it doesn't work well for some reason, you can always use MSI Afterburner.
 
Hope that helps.