Just to clarify, when you say
What exactly are you referring to?
Is it L1 only (single frequency) GNSS units?
The Here+ is a single frequency GNSS unit.
If it is then what you are seeing is about as good as it gets for single frequency GNSS units.
It only when you go to multi frequency that you will start to see improvements in positional accuracy and lock time.
You have probably seen these topics but I am just throwing them in here, there maybe one or two you mightn’t have seen.
RTK and general GNSS inaccuracies
A bit more in-depth here
Finally Spilling the Beans on RTK GNSS
An evaluation of Here+
Arducopter RTK GPS: Quick position and altitude precision evaluation
RTK - Useful or not?
A good comparison
Quick Here+ vs Reach vs Septentrio RTK
RTK GPS Precision Navigation
And a good write up by Tridge