The frequency of the diagnostic settings depends per service and logs. Usually for most metrics is every 1 minute at lowest. Diagnostic logs do not have consistent frequency as they are available when actual log is generated. I do not see why you would have requirement for 1 second frequency of metrics. First it will be way more expensive to retain those and second there is no alerts that can act every second.
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No matter which third party monitoring software you are looking at those will still be using Azure Monitor metrics as bases for their monitoring so the result will be the same.