It doesn't matter how you hold the joycons. Seperated. Attached to the grip or attached to the Switch it self.
They are, by far, the worst controller I've ever had to use for a major system. Everything about the joycons suck. They're too small. The Buttons are small and clicky. No button feels "right" to press and they have no travel time. The analog sticks are way too small, especially to aim with. The B button is too close to the right stick. Pressing the minus button takes way too much effort. The D pad is garbage for everything. Using a PS5 or Xbox controller after the Switch is like taking off your work shoes and putting on your comfortable slippers.
The joycons are trying to be too many things. A handheld controller, a standalone controller, separate controllers and a controller that is both for one and two players. it tries to do too much, and that's why it sucks at everything. I fucking hate these things.