Antibodies are large proteins of the immune system that neutralize intruders, such as bacteria, viruses, fungi, and parasites. There are five main types of antibodies: IgA, IgD, IgE, IgG, and IgM.
To assist you in understanding IgG, IgM and IgA, I found some good articles and videos which do much better job explaining the differences than I can. I hope you find them beneficial.

IgM = Immunoglobulin M antibodies.
https://labs.selfdecode.com/blog/immunoglobulin-m/
Waldenstrom Macroglobulinemia cells make large amounts of a certain type of antibody (immunoglobulin M, or IgM), which is known as a macroglobulin. Each antibody (protein) made by the WM cells is the same, so it is called a monoclonal protein, or just an M protein.
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This video shows the differences between IgG and IgA serology tests and what the results can mean.

Though slow and as exciting as watching paint dry, this video lists each of the Antibodies, their structures and functions.
https://youtu.be/VctTbhhw8do
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In reference to the Kappa and Lamba light chains, they are primarily used in the typing of myeloma patients and determining the degree of disease in MM, B-cell Lymphomas and W/M patients.
This article helps give an understanding of a light chain and how the information is used in diagnosing blood disorders.
https://www.myelomacrowd.org/myeloma/community/articles/kappa-lambda-light-chain
There are several National Institute of Health articles on using light chain in determination of B-cell lymphoproliferative disorders.
https://pubmed.ncbi.nlm.nih.gov/16740039/
https://www.cancer.org/cancer/waldenstrom-macroglobulinemia/about/what-is-wm.html
I know you have WM and B Cell lymphoma. How have you been doing since your Rituximab infusions? Have your symptoms progressed?