honestly, what i've done is just turn on cheats teleport to bandit camps ctrl alt f4 to kill them all then teleport back to my regular location not taking any of the loot etc as to not really influence my position.
If the vassal loses land he blames you for the loss for whatever reason and will lose ~50 relation with you. Giving anyone settlements or castles relation is broken atm AFAIK. Best way to keep them happy is spam influence support.
Personally I took 4 cities and some castles before recruiting vassals. Amassed tens of thousands of influence so that I could negate losing vassals. I basically just spam influence towards my vassals to keep them happy. It's also important that you are giving lands to vassals that already have lands near that land because it's easier for them to defend.If you give them a land in Khuzait territory and then one all the way to the west they will lose it because of travel time.
Quick edit: Don't recruit clans that have 1 or 2 members. They can't defend anything and never have the men to do anything. Any clans with a leader and 3 vassals are the best as they can actually create armies and numbers to defend their lands properly.