Chris,
Are you planning to buy over there, rent ... or ship your own bike over?
If you're doing a long enough tour then might make sense to buy there. That's what I did. I looked at ALL options and buying was the cheapest and least hassle. (for me)
I had a hard time finding any dirt roads at all ... but wasn't looking all that hard. Around Andorra, parts of Spain and Portugal there are some dirt and gravel roads.
I toured a bit of UK (where I found my '99 Tiger), lots of France, just a bit of Italy and Germany, lots of Spain, Portugal ... and a tiny bit of Morocco. If you want dirt ... jump the Ferry. It's easy, pretty fun, lots of dirt roads (Pistes)
All the bikes you list are fantastic. I've ridden the Explorer a couple times, loved it. But she's a BIG girl. A handful on super steep downhill decreasing radius turns. Super comfy I thought, but grinds down with heavy lean angles.
Never ridden the new Trophy. Owned a '99 Tiger (that's the one I bought in UK, did 25,000 miles Touring Europe) I now own a 1050 Tiger here in USA.
If you like tight twisty roads (Alps, Pyrenees) I'd go with a lighter bike. (800 Tiger?) If doing all ON ROAD, also consider the 1050 Tiger. Fast as the Explorer, cheaper (if buying 2nd hand), great brakes and unlimited lean angle. Great value IMHO and not bad on fuel.
Stock Triumph hard bags work fine for me on my 1050 Tiger. But I don't camp, just Hotels, fairly light load. In Europe I used soft bags and a top box on the Tiger. More than enough room on my two, six week trips.
If money is no object then get whatever bike suits you. But if it is a consideration, think about FUEL and the fact it's about $8 a US gallon. Not sure how that translates to Liters ... but it's really really expensive. NONE of the Triumphs are very good on fuel. Even the 800 is down around 42 to 45 mpg.
My 1050 Tiger gets 45 riding hard, and as high as 50 mpg going easy.
I did two big Europe trips on the '99 Tiger shown below. Left the bike with a friend in France for a year, came back, did another six week trip, then off to UK and sold her off. In the end, the bike cost me very little ... WAY less expensive than renting. (storage was free)
Good luck.
My Tiger in France (soft luggage left at Hotel) Note "custom" card board wind screen! ... it worked!