Ok that kit is a Miners Den supplied product (not Minelab).
https://www.minersden.com.au/Miners-Den-Bluetooth-Kit-MD-21The description on their website doesn't give enough detail in order to give you any 100% good advice.
You need to contact Miners Den & ask them for the specifications on their kit so as to fully understand the best option in Bluetooth headphones to suit it.
With these type of Bluetooth rx/tx devices "low latency" can be misleading as it can vary with many still not low enough for some to not notice the delay/lag (latency).
Ideally the device should really have the aptX low latency codec then you would need to find suitable headphones that also have aptX low latency like Minelab headphones ML80 & ML100 here:
https://www.minersden.com.au/minelab-bluetooth-headphones-suit-equinox-series
https://detectorist.com.au/products/gpx6000headphonesml100?_pos=1&_sid=8438f9a4f&_ss=r
If the Miners Den kit device doesn't have the aptX low latency codec then pretty much any Bluetooth enabled headphones should work but may have some noticeable delay/lag. It can unfortunately be a bit hit & miss trying to get a good matching set that won't lag too much.