traffic addons and scenery addons

if you put on a traffic (My Traffic) addon to FSX, can you put all the traffic effects to a minimum that were already on FSX? so it will minimize the bad effects?
also, can what i said above refer to a scenery addon such as REX?

Some add-on AI traffic is easier on the machine than the default, REX takes power away from other slides, it takes a better machine.

can anyone help me out with adding scenery to fsx i recently downloaded balears(spanish islands) and followed the instructions, i extrcted the files to my folder for fs downloads and then copy and pasted the scenery and textures in to fsx correct folders but when i go to start up fsx and go to add on scenery it wont add

Right click.

http://social.technet.microsoft.com/Forums/en/w7itproappcompat/thread/f4d60061-c75a-4296-8aba-b48320ea03d2