Newuserherehurry I've heard that you can relock the bootloader after you finish the installation to make sure evey app works perfectly, is this true ?
Yes, you can lock the bootloader and yes apps (including banking apps) are compatible.
There are some app developers, tho, that decide to rely on Google libraries to check on the the OS.
If this is the case, it might happen the app behaviour is to arbitrarily stop working.
There is a list you can read about compatibility, here.
Newuserherehurry does GrahpeneOS have any "ties" to google ? Can i use it without installing gapps ?
By default GrapheneOS does not have any Google app installed.
If you don't need any service from the gapps, you can just skip the optional installation and the system is already de-googled.
Newuserherehurry an i expect the custom rom to use the full potential of the pixel phone without any issues, i know that the camera depends more on the open-source camera apps but I'm also looking for a good recommendations
As you said, the quality of the pictures relies on the app you are using.
If you are not happy with the default Camera App shipped with GOS, you might as well decide to install the Pixel Camera.
In GOS you have a better and a more granular permission system to help you sleep at night even with a Google Camera :)
Newuserherehurry i don't really think I need to explain this
As a regular Android OS you can install whatever launcher you prefer.
Keep in mind that if you start to use the Private Space or the Work Profile, they must support it, but this is true for every Android OS, it's not a GOS thing.