Loved my 9 days in Selina Porto. The staff were all so friendly and I never had trouble with getting help from anyone.
Cleanliness - the rooms were cleaned daily, I was in a 4person female dorm
Noise - nothing unbearable. I work remotely 2-10pm and the bar outside the bedroom is loud, but if you're used to city living you'll be fine with the noise. Goes until 2-3am. I was fine without earplugs and the hostel bar was right outside.
Safety - never felt the need to lock up my stuff in the room, maybe I'd feel the need in a larger dorm but not in my 4person which had people rotating every couple days during my time there.
Location - so easy to get to the sightsee spots! Basically everything felt like walking distance. Plenty of cafes/bars nearby with some remote workers and often very busy.
Working remotely - This was a little hard. I initially thought there were more spaces for me to work throughout the day without having to pay extra for the coworking office space a block away. However the hostel bar/restaurant requires customers so it's not necessarily open for endless use. There is a space for hostel people where you can sit without buying a drink/food, but its way at the back and in direct sunlight so it wasn't good for working. There are a couple seating spots by reception, a cute small attic library with pillows, the dorm, and kitchen (if empty) for working spots. Realistically if you're working full-time like me, it's better to just spend the extra 9 euros to have a hotdesk in the coworking office.
Events - Selina hosted or was linked to many events which I enjoyed. Pilates & Yoga was included and great way to start the day. Pub crawl, walking tour, vineyard tour all had additional costs but all extremely worth doing!
I'd absolutely recommend friends to stay at Selina and I hope to visit their other sites as I travel.