I was surprised it didn't just auto sort itself out after putting them into the grip..It's the same result in the end, but if you're someone who sells your games later on then it might be better to buy the physical Switch 2 edition (assuming you don't already have the Switch 1 game).
...and yeah as above, if you have the premium Online subscription (Online + Expansion Pass), the upgrade for the switch 1 game is available for 'free'. The upgrade pack is £7.99 otherwise.
I think in that case you'd go to Controllers > Change Grip/Order from the home screen
