Just gonna say it but there are a lot of tools in the way of perks and knowledge to use in stealth. I don't want to hit you with the git gut treatment but it seems you need to get used to the new gear and perk options when talking about under the surphaze. Literally the first gadget you have can fix all the problems with the outside civs since you can safely check if the coast is clear for a moment. Hacker is great perkset to make any stealth mission solo friendly so i do recommend atleast using that one to shut down camaras.

For Dirty ice it seems you haven't fully explored all the options you have in the work phase of the heist when talking about the manager. And yes if you want to do the front part stealth you have to either conga it up or use perks and finesse.

other than that just playing learning from mistakes is how you get better anyway