About the windows managed pagefile size

When windows increases and decreases the size,does it actually creates a file(writes to the ssd)
For example if windows set it to 8gb and at some point doubles the size even if windows is currently not using not even close to 16gb,does iy actually writes 16gb to the ssd

Is it better to set a fixed size than letting windows constantly increase\decrease the size
And also does it matters if I move the page file to another partition if that partition is part of the same ssd that the windows is installed on

If you had a hdd I would say to just disable it, but as you have a ssd, I would just leave it as is - dynamic sizing - unless you’re getting frequent BSODs

I don't think it writes any data to the file. Windows just increase or decrease the reserved dusk space so no other applications can use it. Like in a restaurant where you connect and reserve two or more tables if you are two many friends but only one if you are with your family.

And also does it matters if I move the page file to another partition if that partition is part of the same ssd that the windows is installed on

If you have enough free space on the SSD I would leave the page file on the SSD to make the computer faster. It makes no difference if it is on the Windows or other partition as long as you have more than 40-50GB free (having just enough for the page file can make the computer slower). But if you move the page file on a mechanical HDD it will have slower access and make the computer slower when the page file is used.

Best to leave it where it's by default or it can get confusing to system.