One that can do both Low & Hi Pressure…
Or would you say one for MTB and one for Road is better…

Also, I don't normally camel back it, prefer to stick it in my back pocket, but open to suggestions

Bought a Lezyne Road Drive recently for precisely this purpose. Bit big for back pocket though.

V good, but supplied adaptor is presta only, contrary to what the chimp behind the counter at EBC told me.
Have now bought a new dual adapter, complete with built in pressure gauge, but would probably go for the Pressure Drive which comes with the dual adaptor if buying again.