Wonder how it will play, if it just continues on your run?
When I did my full run (didn't complete the main story until the two DLCs were out) of everything, I did it on death march difficulty. It was fairly brutal in the first 20-30 hours, but reason I did it was because on anything less, I had learned on my previous tries of the game (gotten around 40 hours in each time), it was too easy. I avoided any and all exp bonus items and such.
Still, past around 40 hours it is trivial. Past 50, you get so many grey quests that there are mods for it. But again, exp for what? More levels to become even more OP?
Maybe if you just do MQ it will be ok, but for someone who did everything I could find before progressing main stuff, the game ended up having a very large portion of just pressing X. Which isn't just a Witcher 3 problem. If anything it shows how good the setting/story was as I actually wanted to complete it and see everything even if the gameplay became very boring. I remember Gwent being fun though.