What GPU is active and how to switch between them?

I installed linux mint yesterday and I have some choppy scrolling issues that I think, that is because of the graphic card.
I want to know which graphic card is in use.
I tested a lot of commands and tools. Let’s have a look at some of them:

glxinfo, lspci, nvidia-smi

neofetch result

system info

Another command I used is lshow:

ehsan@ehsan-Lenovo:~$ sudo lshw -c display
  *-display                 
       description: VGA compatible controller
       product: Skylake GT2 [HD Graphics 520]
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:128 memory:92000000-92ffffff memory:a0000000-afffffff ioport:5000(size=64) memory:c0000-dffff
  *-display
       description: 3D controller
       product: GM108M [GeForce 920MX]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=nvidia latency=0
       resources: irq:131 memory:93000000-93ffffff memory:80000000-8fffffff memory:90000000-91ffffff ioport:3000(size=128)

As you can see glxinfo shows that NVIDIA is installed.
lspi and my system info shows that intel skylake is running.
neofetch shows that I have 3 GPUs!

It is confusing for me. I have three questions.

1. Which GPU is active right now?
2. How could I switch between them? For example how could I use NVIDIA all the time?
3. Which GPU is better to use?

>Solution :

I can see NVIDIA driver is running. So you could check which GPU you are using with prime-select:

prime-select query

This tells you if you are using NVIDIA (nvidia), integrated graphics (intel), or a combination of both (on-demand). You can choose one of them by running prime-select with one of those keywords. For using always nvidia:

prime-select nvidia

Which one is best for you depends on how do you want to use the GPU. I personally choose on-demand for not loading too much the GPU and use it for training Deep Learning models. If I would use the computer for gaming or stuff like Google Chrome with GPU acceleration, I would set it to nvidia.