tinovack, a WDH is NOT on the trailer, it's what you put into the receiver in your tow vehicle to pull the trailer. It includes a towing ball and some kind of weight distributing spring bars that may or may not include chains to connect them to the trailer. The WDH may or may not include built in sway control, which I think is a must have, even though the HiLo is not particularly subject to sway. Trailer sway can, and has, caused both trailer and tow vehicle rollover and it certainly causes loss of directional control that can lead to other types of accidents.
There are many kinds of WDHs, mine is the Equil-I-Zer brand. Here's a link to their website:
https://www.equalizerhitch.com/ It has built-in sway control that does not have to be dis-engaged when backing up (some kinds require this). You can get these hitches online from many different sources, so look around. You basically want one that has the capacity to tow the weight of your trailer and that can manage the tongue weight of your trailer. You should choose one that doesn't exceed the tongue weight by too much, so if your trailer's tongue weight is under 600#, a hitch that could support 800# would be fine. If you get one that is rated for a very high tongue weight, it will give you a harsh ride and, of course, cost you more.
Personally, I think the safety chains that come on the trailer are fine, but if yours looks to be degraded, by all means, replace it. I have no preference for bolt-on vs welded.
- Jack