Yes! The Neutron is so compact that it can easily fit in your palm - its just 3.5cm wide!
No, you can fast charge your mobile using any 1 single port. Type C which is PD20W OR USB A which is 18W QC3.0
Yes, It is ok to connect device which needs less power to type C, As your device will only accept required power from the adapter.
Don't worry as charger is working on full capacity it is normal to observe some temperature rise but it will not affect the performance of the charger.
5V 3A = 15W power will get divided between the 2 ports
Yes, when your device will reach 100% - it will cutoff power automatically.
You can mail us on firstname.lastname@example.org with a video showing the problem and an invoice copy and we will be happy to help out