Quick answer: Astromechs are part of Zero Company's playable/operator archetype mix. The historical pre-order bonus, the Crystalline Astromech Cosmetic Pack, unlocked an R3 droid plus translucent crystalline heads for R4, R5 and BR-1 variants.
Astromechs are more than background props
EA and StarWars.com promote Astromechs as one of the character archetypes that can join tactical squads. That matters because the game is built around unconventional Operators rather than only humanoid soldiers. Droids participate in the same mission structure while interacting differently with selected support mechanics.
Crystalline Astromech pack
EA's pre-order guide says the pack unlocked the R3 droid and translucent crystalline Astromech heads for R4 and R5 variants and the BR-1 droid. The pack was advertised as a pre-order bonus for both Standard and Deluxe pre-orders before the August 27 launch.
Because the game is now released, current buyers should check the live store description instead of assuming a pre-order cosmetic automatically comes with every copy. Historical bundle documentation explains what early buyers were promised; it does not guarantee present-day retailer entitlements.
Creating and customizing droids
Official help material for missing/pre-order content directs players through the character database/customization systems to access owned Astromech content. Appearance, personality/dossier-style choices and variant selection give the droid an identity inside a roster that also contains authored characters and custom organic Operators.
Healing difference: Medpacs
EA's Medic specialization guide explicitly notes that Medpacs cannot be used on droids. This is one of the most important gameplay notes for an Astromech-heavy squad. A support plan built around organic healing should not be copied without checking whether each utility actually applies to a droid.
Are R3, R4, R5 and BR-1 different combat classes?
The pre-order guide describes the crystalline items as droid/appearance content rather than four separate standard combat Specializations. Do not infer unique stat packages from the cosmetic names unless the live character database explicitly shows different gameplay rules.