M protein is one, light chains is another. It also depends on what kind of myeloma you have. I am sure there are more tests that I am missing.
The good news is you are responding well 👏

Blood The key important kappa quantities free light chains.
Lambda quantitive free light chains
Kappa/lambda free light chain ratio.

And same with urine.

I’m my case,
A global check has been performed plus each three months follow ups. Of proteins
:
the urine (urinalysis with microscopic proteins, protein creatinine ratio, random, Microalbumin Random.
Urinalysis with microscópics, and blood tests: kidney panel, creatinine, albumin, phosphorus, calcium, osmolality calculated, anion gap, urea nitrogen CO2, Total, Chloride, Sodium, Glucose.
Electrophoresis, immunofixation):
Blood and urine.
Protein electrophoresis Interpretation.
Kappa, and Lambda, and the free Light chain ratio.
Viscosity , serum
Metabolic panel.

Follow ups blood tests.
Bone density.
PTH
Intact and calcium.
Vitamin 25 Hydroxy.
PTH, Intact,
CBC with differential.
B12
Folate
MICROALBUMIN Random.urine.
dexa bone density.
POCT whole blood comprehensive metabolic panel.
Protein total (urine) immunofixation
Total protein
Platelet function.
Hepatic function.
Lipid panel

M Spike is the main one thats the tumor market
Then ya look @ what myeloma you have IGA IGG IGM