Would this work with a Dymo LabelWriter 450 Twin Turbo? Thank you!

The RL2897 is a 2.125" x 2.75" label intended for DYMO brand printers. This is the same size and configuration as DYMO's 30258 label product which can be used in the Dymo LabelWriter 450 Twin Turbo.

Does this need any heat to apply to desired packing?

The Weatherproof Direct Thermal (DW) material is produced with pressure-sensitive adhesive. Heat is not required for the adhesive bond when applying it to your surface.