So, I want to do some martial arts, for self defense. Ideally one that will be useful without giving me CTE, or any long term bad stuff, even though I feel this is already asking for too much 
I don't live in the U๐๐ so gun related stuff isn't really an option.
I'm somewhat heavy, with a year of experience in lifting, and my cardio is not the best, but I can do long walks (of 1 or 2 hours) before getting tired.
I'm going to move to a bigger city in September, and there's a lot of stuff available, so you can comment on the more niche options.
So yeah, any advice from your experiences is welcome lol
If I had known people started arguing over my post I wouldn't have made it.
As someone who does neither if you're worried about ICE I would learn aikido and Brazilian jiu jitsu so that you're extremely familiar with locks, throws and grappling, you will learn how to get out of their grasp while also breaking their limbs
I learned literally one aikido thing when i was a child from reading a book and based entirely on that one thing (a quick sidestep inward with a light push on the other person's chest (push forward and to your left) while you pull their right arm towards you, throwing their ass to the ground) it seems to offer really quick yet simple and effective techniques like that
Do boxing for exercise (best cardio you'l get) and some striking experience but don't plan on fistfighting ICE, plan on throwing their asses to the ground as hard as you can or breaking a limb or two so you can get away if they grab you
i just read your post saying you're not in the U.S. so idk why i framed my response from "if you wanna fight ICE" but im gonna leave it as is