This mock-up was done in PowerPoint and meant to fit on a 4x6 index card. I haven't bothered printing it yet, though.Yep, this is exactly how I do it for my players. I usually list their proficiencies with tools in the skill list and put their armor/weapon prof in their trait section.
Its not too big. Should you print it now (I usually use the large template instead of the 2 columns one), it would be probably the size of 1/2 a sheet of paper, maybe less. Maybe Warlocks and Artificers would be bigger because of their Invocations/Infusions?
EDIT: that also depends on your eyesight. The one you posted is overly large for my needs, but some of my players would indeed require a larger print size.
I have to discuss it with the player on Saturday and find out what works best for him. It might just end up being a combat cheat sheet or index card, a proficiency one, a spells one, etc.