I find appguards configuration confusing
You are not the only one. You are with the 99%.
I cannot recommend Appguard -- even though I have done beta testing for them in the past, and I know the program pretty well -- because you need inside information in order to configure it properly. Otherwise, you can easily shoot yourself in the foot.
OSA is much better. If you want a paranoid setup, just enable all advanced settings, and make exceptions when you get prompts. You might need to use wildcards in your exceptions.
And use
@Andy Ful's ConfigureDefender tool to tweak Windows Defender. There are some powerful settings in there, you just need to activate them.
I am not pushing this third suggestion, but maybe you want to look into
@Andy Ful's complete configuring tool, called Hard_Configurator. It is very powerful. But it is not install-and-forget. It will give you a very effective default/deny setup, similar in many ways to Appguard. Both use Software Restriction Policy. Appguard is third-party, and H_C uses the built-in Windows SRP.