This is my elaboration on Round Trip Latency of Helix hardware used as audio interface based on research on closed fb group
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: