Photography Plan - Which apps are included in the "6 Free Additional Apps" ??

In other words, it isn't 6 apps that you choose, it is 6 apps that Adobe choose. Illustrator would be $20-$30 per month extra.

Creative Cloud Photography Plan -- approx $10/month for 12 months. Includes the very latest versions of these great products & services:
-- Photoshop CC and Photoshop on iPad
-- Lightroom on desktop, mobile and the web
-- Lightroom Classic
-- Portfolio website + hosting
-- Spark with premium features
-- Bridge
-- 20 GB cloud storage (upgradable to 1 TB).

-- Companion mobile apps for iOS and Androids on Google Play and Apple stores.
https://www.adobe.com/creativecloud/photography.html

Illustrator would be by separate subscription.

No, Illustrator is not included, but you can download the trial.

See here:

https://helpx.adobe.com/creative-cloud/faq/CCPp.html#:~:text=Adobe%20photography%20plans%20offer%20the,1TB%20of%20photo%20cloud%20storage.