Shimano hubs are grounded to the fork. If your touring bike uses an SP hub, they are not. That means you might be able to be a bit less careful how you wire a bike with an SP hub.
Taillights, dyno powered lights do not flash. If you want a flashing taillight, you should stick with battery. I initially stuck with battery taillight for that reason. I often use flashing taillight in daytime.
I got my first dynohub in 2013, not for lighting but predominantly for touring and charging up batteries, etc. I use my headlight so little for touring that I am considering not putting a headlight on my bike on my next tour, thus my dynohub would be used exclusively for charging devices. I would carry a small battery headlamp that I can strap on if I have to go through any tunnels or ride in fog.
That said, for riding around town I leave my headlamp (and taillight if fitted) turned on when not charging batteries because the extra drag on the hub is so minor that I can't feel it, so it does not hurt to have it on.
I eventually got a dyno powered taillight, not for primary use, but as a secondary to my battery powered (flashing) taillights. I like the Secula Plus, but that is not a rack mounted one so if you mount a light on a rack you would be looking for something else.
For charging when touring, some devices are very picky about their elecrical source, others are not. Some people can plug a phone or their other devices directly into something like a Sinewave Revolution without using a pass through cache battery, but some devices need the pass through cache battery to work well. More at:
https://www.cyclingabout.com/best-dy...fer-batteries/
My GPS will not charge off of my Sinewave without a pass through cache battery. The batteries I use for that purpose are no longer made, so I am not saying which ones I use for pass through cache battery purposes.
And some people just use a really big power bank that can store several days worth of phone charge. They charge the power bank when riding, and at night charge their devices off of that power bank. In most cases a powerbank does not need a pass through cache battery, so that simplifies things.
But in most cases when touring you are best off leaving your phone in airplane mode or off.
Most, headlamps and taillamps used for dynohubs have a vent hole in the bottom. If you wash off your bike with a sprayer, that can be a problem if you are not careful. And if you do not have fenders on the bike you should be concerned about tire spray throwing water on the bottom of the lights. But, dirty bikes are less likely to be stolen so ... ...