when I first did a map with pack size, I died a lot. 1 vs. 10-20 monsters? so unfair! eventually, I learned how to craft a little better, and it was the monster turn to say ‘nice try, loser!’. 
I had so much to learn. so I stayed away from pack size maps.
now I am doing better, and am beginning to see the good side of using pack size maps.
when I was Ascending for my Perks, pack size maps gave me more monsters to get experience from, and that is a good thing. but after I got my sixth Perk, I stopped using pack size maps, because I decided to see how far I could climb, and I started dying again.
recently, I started using pack size maps again, because I recently went on one just for a change of pace, and all the loot! my thumbs are hurting again from clearing out my bags, and my gold is going up faster than it was before, and my Feats are turning over faster again. 
for those of you who don’t know, pack size maps give a minimum of +50% more monsters to a maximum of +150% more monsters. that is a lot of extra experience and loot. it also mean a lot of extra fighting. all those extra monster will find the weaknesses in your build, so that is a good thing, but also very frustrating, because when they find your weaknesses, that usually means you’re dead. that just means it is a good time to craft your build to be better than it was before.
having a ton of monsters trying to put your head on their trophy wall sounds like a Bad Idea, but if you can defeat them instead, then you have an Opportunity to get a bunch of loot to make awesome gear with. 
packsize is always a good idea… unless your hardware melts. 
What is max number of pack size map?
150%
I am not sure, but I think if you can kill the monsters faster than your device can freeze… 
. a few days ago, I added +10 all skills to my gear, and I love it! 
I have been using non wizard special skills on my OH, and the +10 has made things so much better! using Scalp on my Orb to clear pack size maps, and I think I will keep it. plus, I think I finally figured out how Ascendent + Arcanist works, and clearing pack size maps is becoming really fun.
If you’re trying to climb floors, than you might want to stay away from pack size. If you are farming, then definitely use it. Use the diamond to roll a pack size that is in the area you want to play. How high can it be and you still can beat them? Golem also had a great point, you need to be aware of how high could freeze your system, or create lag. Stay under that as well. Use trial and error and see where he right percentage for you on that floor.
storm pack sizes
Poison master race. Packsize I use all the time these days , including floor climbing. Although its not needed as much for floor climbing but for farming, Its super helpful. My reasoning is that I love seeing insane DMG numbers and so many frozen explosions or poison clouds.
The only downside to pack size map is the one with furies enemy since their meteor landing can cause a lot a pain for you if you not get away in time, especially when if their rain down in narrow area with less room to move
Does that pack size map have a floor number??
Also if your device just wants to kill itself since it cannot handle a packsize number % setting but at the very least, it’s easy to change the number to something playable. Furies I do agree can be annoying.
@SamuelMG pack size is an affix for challenge maps. if you have a challenge map without the pack size affix, just use the Diamond crystal (Edit: Larimar) until you get the pack size affix. just make sure you are ok with the other affixes, as some of them can be difficult to deal with. Legend and Eternal maps have their own affixes.
right now I just charge through the packs, leading with Twister while spamming Scalp. cool down 60% and Angelic Set (5) helping a lot. I think it is a good thing I haven’t built Golems Ultimate Farming Build yet, as I keep learning things I need to learn with my Farming Build #3. right now I am hanging out around the low 400 floors for farming. I am mostly doing the pack size maps for loot, so it is working out great.
diamond just rerolls already existing affixes values.
umm, I meant Larimar?
It’s awesome this pack size affix.