Is SRAM RED AXS Power Meter, 48/35T compatible with Tarmac Pro Disc – SRAM ETAP I am interested in purchasing specialized "Tarmac Pro Disc – SRAM ETAP" bicycle that comes with "SRAM Force AXS, 48/35T" crankset.  I want a crank power meter and want to know if the "SRAM RED AXS Power Meter, 48/35T" is compatible.
Yes they should be compatible - the difference is in the materials/manufacturing:
SRAM Tech Support - Difference between Force/Red AXS

However, you can upgrade your Force AXS crankset to have power:
SRAM Tech Support - Adding power to Force AXS crankset