This is my elaboration on Round Trip Latency of Helix hardware used as audio interface based on research on closed fb group https://www.facebook.com/photo.php?fbid=10156514192780269&set=pcb.1077888115728194&type=3&theater&ifg=1
This topic is hardly relevant if you are monitoring direct. Helix hardware latency is 1,8ms from AD/DSP/DA (measured for one DSP Path), no matter what buffer or sampling frequency you pick.
If you use another interface for monitoring/recording it is not relevant neither. 
It is 2,70 firmware time.
OSX - you have a choice of two drivers:
1. Multi sampling rate Core Audio driver. You get the lowest latency of 15ms using 32 samples buffer but this seems not to be stable (tested on 8th gen i7) . Safer buffers of 64, 128 samples are at 20ms range.
2. Class Compliant 48kHz driver at 64 samples buffer gives 8ms RTL.
EDIT: I do not know if 8ms RTL is REPORTED by the driver or it can be REAL RTL.
Windows - you have a choice of two drivers:
1. Supplied ASIO driver. Here are my figures for Round Trip Latencies:
21ms on "Small" 128 samples buffer@48kHz
17ms on "Extra Small" 64 samples buffer@48kHz
15ms on "Small" 128 samples buffer@96kHz
10ms on "Extra Small" 64 samples buffer@96kHz - but this setting is unusable because of artifacts.
Bad news for virtual instruments players are 3/4 of RTL is on the output side.
2. ASIO4ALL driver - it is rather overlay for WDM driver, not compatible with Pro Tools.
Round Trip Latencies are:
5ms at 128 samples buffer@48kHz
3ms at 64 samples buffer@48kHz
3ms at 128 samples buffer@96kHz
Good news or virtual instruments players are buffers are 50/50 input/output.
EDIT: I have proven that they are in fact REPORTED RTLs. They are fake numbers!
I made my Windows tests using using Reaper (64bit), desktop Windows 10 PC with 3th gen i5 CPU, 16GB RAM. Reaper session was loaded with 5 Hx Native instances.
CPU usage was monitored with Windows Task Manager and for the same 128 buffers on both drivers was at 30%.
7ms pictured vs mine 5ms is because I switched off additional 32 samples buffers used for latency compensation in ASIO4ALL (for aggregating devices?) Some pictures to back it up: