understanding fio test results - 90th percentiles benchmark - Latency --> avg/stdev?

What are the relationships in storage benchmarking with fio between the average(avg) and standard deviation (stdev) at latency? Avg / stdev at latency is important for sequential or random test? Most I/O subsystems are very well tuned that the standard deviation has little significance for sequential accesses. Furthermore, it is of interest how the standard deviation is with the random test. is that right? I was advised that in cases where the avg/stdev ratio related to latency is 5 %, the system is still problem-free in cases where the system is optimal 10% but at higher rates there is a problem in the system. fio --rw=randrw --name=test_zufaellig_oci --bs=4k --direct=1 --size=10G --ioengine=libaio --runtime=5400 --time_based OCI test_zufaellig_oci: (groupid=0, jobs=1): err= 0: pid=16244: Thu Dec 29 17:16:45 2022 read: IOPS=1313, BW=5255KiB/s (5381kB/s)(27.1GiB/5400001msec) slat (usec): min=7, max=1665, avg=16.39, stdev= 6.30 clat (usec): min=3, max=202186, avg=354.88, stdev=167.22 lat (usec): min=290, max=202206, **avg=371.52, stdev=167.53** clat percentiles (usec): | 1.00th=[ 310], 5.00th=[ 318], 10.00th=[ 322], 20.00th=[ 330], | 30.00th=[ 334], 40.00th=[ 338], 50.00th=[ 343], 60.00th=[ 351], | 70.00th=[ 355], 80.00th=[ 363], 90.00th=[ 383], 95.00th=[ 408], | 99.00th=[ 498], 99.50th=[ 611], 99.90th=[ 1762], 99.95th=[ 2376], | 99.99th=[ 6128] bw ( KiB/s): min= 816, max= 6096, per=100.00%, avg=5263.74, stdev=325.49, samples=10781 iops : min= 204, max= 1524, avg=1315.94, stdev=81.37, samples=10781 ----- AWS test_zufaellig_aws: (groupid=0, jobs=1): err= 0: pid=2960: Thu Dec 29 17:16:54 2022 read: IOPS=315, BW=1261KiB/s (1291kB/s)(6648MiB/5400007msec) slat (usec): min=6, max=107, avg=19.35, stdev= 4.90 clat (usec): min=190, max=113470, avg=1472.25, stdev=2373.50 lat (usec): min=207, max=113491, **avg=1492.51, stdev=2374.87** clat percentiles (usec): | 1.00th=[ 318], 5.00th=[ 347], 10.00th=[ 363], 20.00th=[ 392], | 30.00th=[ 412], 40.00th=[ 429], 50.00th=[ 453], 60.00th=[ 482], | 70.00th=[ 529], 80.00th=[ 644], 90.00th=[ 6915], 95.00th=[ 7046], | 99.00th=[ 7177], 99.50th=[ 7242], 99.90th=[ 7504], 99.95th=[ 7635], | 99.99th= bw ( KiB/s): min= 144, max= 4184, per=100.00%, avg=1262.50, stdev=1493.09, samples=10783 iops : min= 36, max= 1046, avg=315.63, stdev=373.27, samples=10783