They run , sort of ok but on the small ring you will have a degree of chain slap , so if you don’t go much further than 4 /5 cogs down from the biggest rear cog when on the 34 it should work, used it last year in the Pyrenees and at the Fred
Can be a bit slow going back to the big ring , but I suppose that depends where you change back up.
However a 39/34 is fairly close to a 34/30 , 39 36 will be just about the same as 34/32 there’s not many hills about here that you couldn’t get over with those ratios , but the wide range in 36 11 speed might be a pain as rear Mech you ride Shimano do they not all take dinner plates now ?