Hey guys really looking into cutting the fenders on my samurai. My brother and I recently did this on his jeep and found out it is a little harder to do than we thought. I am wanting to know what the best to use is. What will get it done the quickest

A plasma cutter would be the ticket, but not many of us have one.  If you are good with a torch, it won't do too much damage.  And with some care a 4.5 inch grinder with a cutting disk can do a neat job.
It depends on how big of tires you will be running, and how good you want it to look.
A very long time ago we cut these wheel wells out on Drone637's SJ.