All good questions.
Gimp - any version - when first run creates a User Profile. For Windows that is the C:\Users\"yourname"\AppData\Roaming\GIMP\xx.xx folder and these remain even if you uninstall Gimp. You can delete if you want. Run Gimp 3 and it makes a new default set.
You had Gimp 2.10 and got .....\Roaming\GIMP\2.10\ Now install Gimp 3 and get ....\Roaming\GIMP\3.0\
These come with a lot of files and (empty) folders for you to add resources, example new brushes / patterns / fonts .... that are only available for your use.
You have Gimp 3.0.6, use it and get used to the new features. There is a Gimp 3.2 coming in the future, and if installed will make you ....yet another ....\Roaming\GIMP\3.2\
A lot is just practice but Gimp 3 has what are known as layer effects (fx) which can affect work-flow see: https://docs.gimp.org/3.0/en/gimp-using-...fects.html
Until you get used to them, many filters like curves / colorize / desaturate / ..and many more have a merge filter tick box Use that to merge the (fx) and Gimp 3 behaves more like Gimp 2.10
EDIT: Just a note, if you accept the defaults when installing Gimp 3 it does install to C:\Users\"your name"\AppData\Local\Programs\GIMP 3 - for your use only, but you should have seen that when installing.
Gimp - any version - when first run creates a User Profile. For Windows that is the C:\Users\"yourname"\AppData\Roaming\GIMP\xx.xx folder and these remain even if you uninstall Gimp. You can delete if you want. Run Gimp 3 and it makes a new default set.
You had Gimp 2.10 and got .....\Roaming\GIMP\2.10\ Now install Gimp 3 and get ....\Roaming\GIMP\3.0\
These come with a lot of files and (empty) folders for you to add resources, example new brushes / patterns / fonts .... that are only available for your use.
You have Gimp 3.0.6, use it and get used to the new features. There is a Gimp 3.2 coming in the future, and if installed will make you ....yet another ....\Roaming\GIMP\3.2\
Quote:.... I have had problems with painting on layers and using layer masks.
A lot is just practice but Gimp 3 has what are known as layer effects (fx) which can affect work-flow see: https://docs.gimp.org/3.0/en/gimp-using-...fects.html
Until you get used to them, many filters like curves / colorize / desaturate / ..and many more have a merge filter tick box Use that to merge the (fx) and Gimp 3 behaves more like Gimp 2.10
EDIT: Just a note, if you accept the defaults when installing Gimp 3 it does install to C:\Users\"your name"\AppData\Local\Programs\GIMP 3 - for your use only, but you should have seen that when installing.