According to description of Remaining Work field available here https://learn.microsoft.com/en-us/azure/devops/boards/queries/query-numeric?view=azure-devops#fields-used-to-estimate-and-track-work I set my ProcessConfiguration with "h" for hours.
Since Remaining Work is declared as double, I guess that is possible to enter in this field hours but also minutes. Is it ok to set "half an hour" with 0.5? "10 minutes" with 0,16 and so on?
Yes, you could track it like that. I think if you try to track individual times less than a quarter hour it brings on a lot of other problems though. If you have multiple people working on the same task, the out-of-box functionality is not great for tracking that. If you want to roll-up tasks time to a feature or PBI, the roll-up is not that great.
I've worked on projects that were billable to different customers and we billed in quarter-hour increments. We tracked the time for billing and used a paid extension, Timetracker. It was good at managing to the level of detail you might desire based on the wording in your question.