One way to do this will be to monitor the writes/sec for weeks or a month and then come up with a number based on what the max values that you are seeing. Obviously this is a rough guide, and as your workload changes you would have to adjust the threshold as well.
You could also use disk benchmarking tools to test the throughput of your disk subsystem. ...
100% RAM -- You are probably swapping, which is terrible for performance. Lower innodb_buffer_pool_size a little to avoid swapping.
200% CPU -- Poor indexes and/or poor formulation of queries. Please provide some of the queries and SHOW CREATE TABLE; there may be a quick fix.
"out of order" and "different value" -- Either a bug with the collection ...
I think what you are looking for is Query Store, but this is available only for SQL Server 2016 or higher.
For SQL Server 2014 or lower, you can set up an Extended Events (XEvents) session to capture the queries running longer than X amount of time. XEvents are really easy to use and quite intuitive, the only thing you should pay attention to is how much ...
Try SSMS's Activity Monitor:
Or try to use perfmon: