Multi-Sided Tokens & Alternating Stats:

Confident this question's been asked before but I couldn't find it in the archives.  Is it possible to assign different stats to different sides of a multi-sided token or is the multi-sided-ness of the token strictly cosmetic? Looking to make one master "familiar" token, which is easy enough, but I'd love it if I could program in the specific stats, particularly for the Chain Pact fighting familiars. Thx!

It's strictly cosmetic. If you are a Pro subscriber, you have access to scripts that can trigger changes when token side changes, but short of that, it's purely cosmetic and you have to handle it manually.

The non-Pro/API way to do this is very similar to the Pro/API way.  Create the multi-side token, and also create all of the 'characters' for each type of familiar/stats.  Pull out the token, and set the 'represents' manually (open the token) to whichever character/stats you want.  If/when the familiar changes shape, just change the 'represents' to the new character/stats. The Pro/API way simply allows you to change the side of the token and 'represents' with a macro query/chat menu.

If you don't mind sorting out the macros yourself, it is possible to have a macro on one character sheet that pulls details from another one, I used that technique before I got a Pro account for a werewolf, on its standard human form character sheet i would write a macro, for an attack say, that pointed to the Wolfman|Strength characteristic on the Wolfman sheet, for when it changed form and set that as a token action or chat menu button.  it took a bit of work to set up, but it did do the job.  You just have to remember to change all the sheets when you gain experience.

Something I do for when I play druids- I make a multisided token with the different forms I want to use, then create heavy armor inventory items (this is the 5E by Roll20 sheet, BTW) and give them attributes to alter my Str, Dex, and Con up or down as appropriate to the new form, with the AC set for the animal's AC. Then I create custom attack (and occasionally skill) macros for the animals' attacks. I make a whispered chat menu, one for each form, and it includes the form's stats and buttons to run the attacks/skills. The only thing my DM has to do is alter the size of the token, as appropriate.