Sigismunds camp [KCD2]

I just paid 500 Groshen to get into Sigismunds camp, I just arrived in the region and besides helping the red devil I have done nothing at all. My question is can I just do the side quests that have been offered to me in sigismunds camp without them actually knowing im not apart of their army? I haven't done anything else in the region and I don't want to screw up straight away by doing missions for the enemy right away.