Highly recommend the Prodigy P2 or the P3, both by Tekonsha.
Activator seems to be time delay = paperweight.
Good practice is to use trailer brakes if you have them. They will help you stop shorter in an emergency.
As far as when they are required, my opinion is if the combined weight of both truck and trailer exceeds the truck's GVWR, you need them. This is because the tow vehicle's brakes were only designed to stop the GVWR of the truck itself.
You didn't state what you are towing with. But unless you have an F350 or better, you need trailer brakes.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller