Let is know how it turns out
The 2 we installed used flare fittings , no brazing .Follow the directions and you'll be ok. Be very clean, use plenty of nitrogen if you braze and follow the leak check procedure as the manufacturer dictates.
The evaporator on a straight cooling unit may not be rated for such pressure. You do have to look at the rating plate before pressurizing. Otherwise, your right, some leaks are painfully slow even at higher pressures.Just a small note, I've seen many a leak show up at 400+ PSI that wasn't detectable at a lower pressure.
When we do a startup, the installer is required to put a minimum of 590 PSI on the system for a minimum of 24 hours. Then we do a 200 micron evacuation.
I've also seen joints start leaking when they heat up but with a 590 psi test charge the chance of having further leaks is very low.