Welcome To The Family 😊
No way to auto set the levels, depending on the tones the levels will be different to cut through the mix
Welcome to the forum!
2. Does balanced or unbalanced XLR to a PA affect the tone at all?
No (well maybe).
XLR or TRS cables aren’t balanced or unbalanced themselves. It is the equipment they are connected to that is. XLR and TRS allow two pieces of balanced equipment to be connected with a balanced signal. As TS connection on the other hand can’t carry a balanced signal even if the sending and receiving gear can handle it.
The sound from the Kemper will be the same either way but balanced from the XLR output will be 6db louder than unbalanced from the TS. If the receiving input (FOH desk or audio interface for example) has a preamp that is designed for microphones the balanced signal might overload the input and cause clipping of the preamp. This would obviously affect tone even though the balanced and unbalanced tone from the KPA was the same.
Hope that makes sense.
Welcome to the Party!
You may want to look into the Clean Sens and Distortion Sens of the Profiler Input settings.
Also go through these tutorial videos here. Lots of information. And don't forget to read the manual a zillion times. 
1. is there an easy way to level all patches so they all give equal volume - some take the skin off and others can disappear. And can a “global” button be assigned to say increase patch volume to compensate for humbuckers to singles etc?
So the answer is no...but the reasons are actually very logical:
1) You don't always want all patches to be the same volume e.g. solo volume.
2) Volume does not equate to cut. Clean sounds will require less volume and therefore
3) Humbuckers and single coils are not always different volume wise and single coils can cut more than humbuckers and although output can be higher aren't always "louder". plus you dont want to lose the character of those guitars by leveling everything out - so you will probably want a touch more gain etc. Personally I dedicate a performance to a particular guitar if it's that much of an issue, but think about how you manage this with a regular amp??
Balancing volumes is so easy to do and needs to be done with the band at volume. This only becomes a significant problem if using a rig per song and have hundreds of rigs to manage (which I feel is the wrong way to set it up anyway). Personally I only use about 5 different sounds/rigs and so this is not an issue.
+1 agree with V8guitar + :
- The problem is in frequencies ; the dBmeter can indicate the same level but one rig will seem to be louder cause the mids are more present.
