If you want an education on single handed shooting attend one of the bigger NRA Bullseye matches.
https://bulletin.accurateshooter.com...cp-one-handed/
How accurate can a .45 ACP pistol be, in the hands of an expert marksman? Take a look at that target. This was shot off-hand (no rest) with ONE HAND at FIFTY (50) Yards. That’s TEN shots at 50 yards all inside the 3.36″ 10-Ring with eight shots in the 1.695″ diameter X-Ring.* We bet most folks would have trouble matching that with a scoped rifle shot standing.
NRA Pistol Book (March 2016):
High Master .................................................. ......97.00 and above
Master .................................................. ..................95.00 to 96.99
Expert .................................................. ...................90.00 to 94.99
Sharpshooter .................................................. ........85.00 to 89.99
Marksman .................................................. ...............Below 85.00
These are all one handed so you have a basis to compare. Most people that are serious about it can achieve the Master Class. High Master takes a lot of dedication but if your eyes and build are not ideal High Master is very very tough. I am 6' 4" and most of the best shooters are on the short side. They can hold steadier.
As to right or wrong that needs to be settle on the range, however, if they can't do 10 shot groups at fifty yards on demand I tend not to listen to their opinions much. That being said more handgunners tend to do sustainably better with two hands. Like everything there are advantages and disadvantages to both methods.
For self defense two handed allows for quicker follow up shots but I have seen shooters that a pretty good two handed but are pitiful one handed.
What size groups are you capable of shooting on demand and at what distance?