Complete 2021 Trailblazer specifications are still not available. Some have been confirmed and are outlined here, along with other details to expect when the full list gets released from Chevrolet.
Set to be "positioned between the Trax and Equinox," will mean dimensions that fit between the two. What that mean's in terms of overall passenger and cargo volume over the Trax are measurements that range around rivals like the Jeep Renegade.
In the Jeep that is 1-1.8 inches of more front/rear headroom, shoulder room and hip room. Also 4-inches of more legroom like the Trailblazer. Cargo capacity grows slightly.
Knowing the Trailblazer will sit on GM's VSS-F platform will mean we get engine/transmission configurations from vehicles sold on it. Closer to its early 2020 launch, that's expected to be confirmed as two engine options; a turbocharged 1.4-liter currently producing 150-hp and a turbocharged 2.0 producing 230-hp (Trailblazer RS?). Both mated to a 9-speed automatic transmission.
Aside from the usual LS, LT and Premier trims offered, availability of Redline and RS trims have been confirmed in statements from Chevrolet USA. Details are on them are limited. You can expect a similar level of upgrades as found in Redline and RS trims currently offered in other models. In the Redline it will be 17-inch black wheels, upgraded sporty aesthetics and red accents found throughout.