[Aerich]

Not appreciably, no, except in that they add more enemies, who will drop individual treasures for you to pick up. The big money is in various magical (named) artifacts, so you might only get a few extra thousand in total from increased numbers of enemies.

Re: the trap-finding question... Are you waiting long enough?

You need to a) be able to find traps by having enough in the skill and wearing appropriate armor, b) click the trap-finding icon, c) wait long enough to "find" the trap - it will become highlighted in red and d) click the disarm/pick pocket icon then click on the edge of the highlighted trap.