I think since you have absolutely NO experience, you should learn with an arduino uno board. These boards are ready-to use for beginners and include an ATmega328p AVR microcontroller. You can find tons of tutorials on the internet for the Arduino device family and there's a lot to learn. Have fun!
I have normally used the full-swing setting but it is not critical.
The main issue is whether you are using the XTAL2 output for driving other devices (either another MPU or logic).
See page 42:
"This Crystal Oscillator is a full swing oscillator, with rail-to-rail
swing on the XTAL2 output. This is useful for driving other clock
inputs and in noisy ...
If you read the AVR datasheet, it says you can use either low power mode or full swing mode with a crystal of that frequency, but only if the AVR supply voltage is high enough. If supply voltage is too low, you can't use full swing mode then.
I set the arguments line to COM3 like this:
-CC:\Arduino\avrdude.conf -patmega2560 -cstk500v2 -P\\.\ COM3 -b115200 -Uflash:w:"$(ProjectDir)Debug\$(TargetName).hex":i
This seems to have a mistaken shell escape sequence in the port specification.
Typically the specification to avrdude would be of the form -P COM3
For unclear reasons, you are inserting ...
I also doubt parasitic capacitance is the issue here. I simulated a circuit with 100pF to ground (a huge amount) and a faux mosfet gate termination. and only saw ~5mA though it with rise/fall times of 100ns. If your rise times are much faster you will see more current, but according to this post:
How solder inductance affects RF circuits?
you'd be lucky ...
The ones in the picture are standard 2.54 mm pitch.
There are many more pitches than 2 and 2.54 mm. For example have a look at the pitch selector in Mouser: https://www.mouser.co.uk/Connectors/Headers-Wire-Housings/_/N-ay0lo
I found this repository containing some design files and although the board is different from the one I'm gonna use, I'm assuming they do follow the same standard. The pitch on this one is 2.54mm. Feel free to correct me, but until then, I'll leave this as an answer.