If it's leaking at a press in bypass tube, I would replace it and thread to NPT and use Teflon tape, although a good RTV will do wonders on the threads to. Assuming it isn't concours, if it is, I may look for a metric tube every so slightly larger
If it's leaking at a threaded tube, I'd pull it make sure it isn't bottoming before it tightens, and seal it
If it's leaking at the hose, I like the Wittek (factory style) hose clamps far better than worm clamps, they squeeze without tearing up the hose. That being said, if you use them, hold the body of the clamp with a open end wrench and tighten with a 1/4 drive socket and ratchet. It keeps from twisting the body of the clamp
If it is a repop bypass hose with the ribs, you may never be happy. When able on the concours builds I try to talk the owner out of it. However they make it, it's usually soft looks like it will fail even new
As far as water vs antifreeze, I have zero issues with immediately running water then getting antifreeze in it. They do rust quickly with water even though at that point it isn't harmful and of course if someone forgets and the block freezes, it's a bad day. However, if you are seeping rust at all the hoses, I feel like you have a clamp issue, hard hoses, pitted parts or need to tighten the clamps a little better.
I have never sealed hoses, but I wouldn't be afraid of light wipe of white lithium grease or silicone grease, sparingly, or maybe even some non hardening RTV