Wearing all 5 I seem to get a few more silver leaves than my friends wearing one. For a full altar of sorrows I was getting between 3-6 more leaves than my friends just wearing one.
The big difference is when converting the leaves to ashes in the bonfire bashes at max ignitions you get 20 ashes per piece of solstice armor equipped.
FYI For really quick silver leaves with a fireteam and some weapon leveling you can load into the first lightfall mission from the classic replay icon and go all the way to the end. When you get to the drop pods have no one get in and one person switch characters and rejoin and then everyone get in the drop pods and you hit the ground the person that left can reload the checkpoint and everyone rejoin. you’re at the drop pods and can repeat. 15 silver leaves per run wearing 5 pieces + 12% weapon level per run. Won’t be surprised if Bungie eventually patches that or disables it somehow
Max is 30 this year. Assuming you have at least 20 silver leaves and max ignitions you’ll net 20 ash per piece of solstice gear equipped. So if you have all 5 on you’ll get 100 silver ash. You can just equip all 5 pieces once the final boss spawns in, you don’t have to have them equipped.
Sticking together is generally the best strategy, especially playing with randoms. Once you get the throws down there’s only two spots where you can’t throw the ignition charges from where they drop (the alleys to the left and right of where the boss spawns) so when I’m playing with my friends we’ll sometimes split up a bit and I’ll clear an area by myself when I know I can throw all 3 in myself before rejoining them