I've always wanted to go to all three because they all seem great. They'd be expensive for me to go to. I think if I had to pick one it would be Japan because there's so much to see and do, and the culture is gorgeous.
It's easy to avoid the nukes ... just don't go anywhere near big cities or military locations ... it's the radiation and nuclear fallout you have to worry about ... so it's best to head to the southern hemisphere and go to places like New Zealand instead.
I just came back from Japan and gotta say it is definitely worth a long visit. The 2 weeks would even be a tad short, but still a great opportunity.
Food is not expensive so you dont "save" a lot on it in this thought experiment, but hotels, especially during sakura time right now, would be a big one. And well, just getting a chance to experience Japanese culture, especially coming from "rude western countries" is pretty great. Definitely gonna go back there.
I would go to the Azores and see what it would take to stay there. I've always found the vibe in coastal regions more agreeable and I've heard good things about the Azores. No need to worry about currency as it is part of Portugal so Euro zone. The weather is fine, not too hot, not too cold. Areas are beautiful.
Only thing is that it might cease to be above water if the seas keep rising.
Albufiera used to be a small town gem about 20 years ago but now the vacationing Brits have turned it into party central and it feels more like a giant disco sports bar now. I saw it first in about 2005 and it had a lot of historic charm. Then I saw it again in about 2015 and it was drastically changed with whole streets filled with sports bars and discos. Be careful in the weekends there because the streets are filled with drunken tourists. It was like New Orleans during mardi gras ..... every weekend! As exciting as it may sound to tourists, the locals absolutely hate it and judging from the last time I was there they hated the tourists, especially the Brits.
Portimao, to the west is a quieter and more Portuguese location with better and larger beaches and more traditional and cultural appeal.
I'd avoid Albufiera because of the bar scene (which can be had anywhere in the world), unless that is what you are looking for.
Seville will be amazing and beautiful .... head to Malaga and Granada if you have the chance. Malaga is beautiful this time of year because there aren't that many people and you can enjoy their huge Malagueta beach next to the city.
I just noticed you said 21 days .... Holy Week is happening from April 13 to 21 this year ... Holy Week is basicaly everything surrounding Easter (the Spanish celebrate it for a week before actual Easter Sunday) ... Seville will have huge events starting on the Monday 13th and last all week until Sunday 20th
Seville has big events but Malaga has the biggest most spectacular gatherings that will last all week ... the city has a population of about 500,000 - I think it was about 300,000 for the city proper ... but it balloons to over a million people on Holy Week. The Easter processions where brotherhoods of people march through the streets all day start on Monday and each day after get bigger and bigger and more numerous processions all week ... it all culminates on Good Friday with the largest processions and about 20 processions marching through the streets ... it's also a 'familyish' event as the entire city will be filled with families, children, elderly, adults, teenagers ... some drinking but no outright partying. But it is jam packed and mobs of people pushing together everywhere. Unless you've booked a place to stay weeks ahead of time, you won't find any place to stay in the city unless you want to pay thousands per night.
The biggest day is Good Friday ... events die off on Good Saturday and Easter Sunday is quiet as it is traditionally considered a holiday that is spent at home with family instead of making people work or participate at a major event.
During Holy Week ... Seville, Cordoba, Granada and Almeria have big events, but the largest and most spectacular of them all is Malaga.
Here's a photo of what you would see during Holy Week in Malaga ... don't let the imagery put you off, those outfits were part of the Catholic Church for hundreds of years before any one in North America used them ... and the outfits and parades come in a variety of colours (black, white, purple, red), and the largest brotherhoods on Good Friday march with the Priesthood leadership, the brotherhood, the congregation, its elders, a full marching band, leading women, alter boys and girls and a float representative of their church (the largest of which weighs about 2/3 tons and is lifted and marched for several hours by a host of 100 men) ...
One of the most famous brotherhoods includes the actor Antonio Banderas, who is from Malaga and he secretly and discreetly joins his brotherhood every year as one of the masked participants.
You got me excited because I've been to this celebration three times and each time it was amazing.
It's known for very hot summers, tropical but it's tempered if you stick to the Mediterranean coast and even more so in the Atlantic coast. It's also got the warmest winter weather in all of Europe on its southern Mediterranean coast.
It's also a first world country so everything works for modern banking, telecommunications, transport, rentals, hotels, restaurants and all services in between. But it also still has deep cultural roots so there is lots of interesting things to see and do. In the late winter there's a period in the year where you can go skiing in the Sierra Nevada mountain peak in the morning and go sunbathing on a beach in the afternoon.
I've been to Spain about a dozen times years ago and it's the best base to travel from when going to Europe. You can connect to everything in Europe on cheap flights from Malaga.
If all expenses are paid I would make sure to find somewhere expensive to go to. I am going to with Thailand since its an expensive flight and while I know its not as expensive when you get there. I have also been watching White Lotus. Why do you ask?
Well if I am going all expense paid I will have some kind of fancy security team to go with me for my back packing videos. I might get a few private boats and plane trips as well. Got to cram as much nature as possible in there
If the goal is to maximize money spent, I'd stay in Copenhagen and hit a few gastro hot spots. It's a lovely city, good for drinking and dining, but whenever I go there, I feel poor.
I'd also consider less costly but equally wonderful foodie visits to Bologna or Girona. In either case, I'd rent a villa. In Girona, I'd stop at El Celler de Can Roca.
I would really prefer just the cash but as much as I hate the environmental impact I could not pass up a free all expenses paid vacation. I would choose japan with one week in Aman Tokyo and one week in Aman Kyoto because I want super decadent high end pampering but at the same time I would just love to see the two sides of japan like that. I guess if it was limited to standard fare I would still do japan honestly. I mean I need to see a bit of these places animes take place.