W Trek in Patagonia — too much for a first multi-day hike?

Since you haven't received any responses yet I'll add just a little- I checked out the link you added and it seems really comprehensive for your general research.
I traveled with a tour this January, so it was the middle of summer. While certainly not the W or O caliber, we had the opportunity for some moderate hiking in both parks.
That wind! Was so intense at times throughout the region and one of the intended trails was suddenly closed as a result. I don't know if that ever applies to the W, but you need to be sure to have really good clothing. (I wore a thick fleece vest under my lightweight puffer and pulled on a wind and waterproof 1/4 zip anorak when the rain came. It wasn't a hiking trip, so to keep to a carryon I improvised.)
But we had several gorgeous clear days, too.
Caveat: the guide kept saying the clear views were quite atypical. Repeatedly he would say, "Normally people don't see this. Only clouds!" OTOH that is true for mountains in general- in Chanonix in June there was a blizzard at higher elevations...and many days I can't see Mt Rainier!
I would definitely go with a reputable guided small group, especially if your Spanish is limited.
I flew into Santiago and out of Buenes Aires. Buenos Aires is simply gorgeous and I really recommend at least a couple days there at the start or end of your trip.
And also, it was my first trip to South America and that experience was so memorable, too. Good luck and happy travels!

This is a hard question to answer for somebody else, even having the experience to give an opinion. Hiking difficulty is highly subjective, I have found. I hiked the Dolomites last year and trails labeled “easy” were challenging to me. I am going back this year, but doing a lot of strength training to try to level up.

I would love to do the W hike one day or the Tour de Mont Blanc, but I feel I would have to train even harder. That is just me though. You know your body and limits best.

If you have hiked in the alps with elevation gain, at a decent elevation, for a moderate distance (say greater than 6 miles) that is a good comp I feel. I think most people do about 10 miles per day on the W. If I remember correctly the first day is pretty difficult with about 15 miles and several thousand feet of elevation gain.

There are better resources than RS to help assist you. I have researched for myself recently. Lots of detailed answers on Reddit or you could read reviews on AllTrails. Plenty of people there that really know their stuff regarding hiking.

Agree with the prior poster that this is a hard question to answer without knowing more of your hiking abilities especially elevation gain and if you are hiking this on your own with your stuff on your back.

I am just in the starting phases of planning the hike of the O circuit next January (the W is a smaller section of the O) - this will be with some friends and I. We are all experienced hikers/backpackers and spend quite a bit of time hiking in the high country in Colorado and sometimes in the canyons in Utah. It is hard to say how you will react to actually hiking day after day even though the W trek is normally only 4 days in length. I would be interested in where you do most of your day hikes, what mileage you normally cover and most importantly how much elevation gain you normally get in on your hikes. You should collect this information in a spreadsheet and then compare to the daily sections of the W trek.

When hiking in CO we may get as much as 4,000 ft of elevation gain in a day which is a lot as we grow older. However, with a backpack that could be between 20-25 lbs on a 4 day trek, even doing 2500 ft in a day is a lot. My advice is to get in at least 1 overnight backpack and preferably a 2 nighter (3 days) where you are covering significant ground but especially with at least 1,500 ft of elevation gain a day.

Have you looked at the accommodations in the park? Are you staying in lodges or paying for tents. Will you carry your own tent and sleeping bag, food and stove or are you planning on renting from the concessionaires. Note - this is not cheap. Food itself will run you over $100/day and renting the other equipment is also pricey. Our plan was to carry our own tents, sleeping bag/pad, and towel and just reserve the tent site. We will likely not carry food other than snacks and buy from the lodges/camp sites.

Note (you probably already know this) - all the camp sites are managed by two different concessionaires and hence you need to make reservations with each individually. This means you need to plan what night you are spending where and book accordingly including your arrival and departure days. Good luck