The keg purge with sanitizer and remaining in keg connection through to racking works really well (especially with a cold crash). I always use that method when pressure fermenting due to its simplicity. I use a 14 gallon kegmenter and a 7 gallon Fermzilla All Rounder as my pressure fermentation vessels usually. The CO2 "catch bag" approach seems fine as to cold crashing - but with spare kegs and pressure fermenting, I don't run into an implosion issue on cold crash.
Alternatively, (or in addition) you can simply hook up CO2 to the fermenter (or purged keg) and push beer to receiving keg through purged lines. I use a spare keg to pressurize with CO2 and purge all lines before racking with those tubes. It isn't perfect and I have no way of knowing/measuring the extent of minimal O2 ingress (indeed some would say the use of packaged CO2 is not pure enough relative to O2 ingress and staling over time), but it is close enough to low ox as I am willing to get on the cold side.