What do I need to look for when choosing a 4 link? Any brand better than others?

Most name brand companies are pretty closely matched. Most kits do not come with heim ends. If you find a four link kit with heim ends, you might save yourself a couple of dollars. Get a kit with the thickest lower bars they make. I like the Smith Racecraft stuff. I bought an outlaw ladder bar kit from them, came with really nice, thick four link axle brackets. Had good prices, too.

Smaller bolts give more adjustment. Reinforced brackets in hole area keep hole from wollering. Quality ends are worth the $$

Get one with an anti roll bar. I like the S&W kits myself.

Yes ARB bar makes a huge difference.

IMO get one with the MOST adjustability you can afford! Some of the kits out there have 7-8 holes in the front bracket. IMO those will likely find you a good place to work with but changes that you make may have a large effect on IC. IMO if you can afford one with more adjustability(smaller bolts or sliders)the better off you will be in the end.

They aren't all the same and don't all have the correct geometry. Buy from a real race car shop, not someone who does street rods and other crap. Look at the brackets offered by Bickel and RJ for up to date designs, i.e. hole sizes, locations and spreads, provisions for shocks, etc. Different units have different provisions for shocks, wheelie bars, roll bars, etc. Get the one that suits how you will be doing your housing. I don't think anyone does them with .750" holes anymore, but avoid those. 1/2" holes with the corresponding tight hole spacing are the best way to go. Don't use junk rod ends.

Make sure whatever you choose has a diagonal, or wishbone of good size. I see decent 4 link kits that have small dia diagonals. They should be same size as the rest of the bars. Basically something the driveshaft can't break if it breaks. No fun going rear wheel steer.