You can read and write (for one request) the config options via the core module "Kernel::Config".
The config object is a base object and thus available in each Frontend Module.
If you want to access a config option:
my $ConfigOption = $Self->{ConfigObject}->Get('Prefix::Option');
If you want to change a config option at runtime and just for this one request/process:
$Self->{ConfigObject}->Set(
Key => 'Prefix::Option'
Value => 'SomeNewValue',
);