Hi, i use on my engi one arclight exothermic rifle, and planning later useing Lees, but need to know it's the only choice or exist better?

There is no "only choice". Use whatever you find enjoyable. I haven't used a single automatic rifle on my Engineer, and he's never had a problem.

some people use rifles, some people use one handed guns with skills, some people use a combination of both with weapon switches, its really just up to personal choice

yea theres alot to choose from just got to find one u like or 3*