This subject is very complicated. I don't know all that much other than what my rheumatologist tells me. It boils down to the following:

"Unlike intravenous dosing, the tocilizumab subcutaneous dosing regimens use a fixed dose (162 mg) over a wide range of body weights."

Good luck with understanding the link that this quote is taken from.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5363244/
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I can share with you my personal experience with taking Actemra. I had an extremely good response to Actemra with very miniml side effects. My rheumatologist is amazed with how well Actemra is working for me. Since it is working so well for me, my rheumatologist seems reluctant to discontinue Actemra.

During the course of my almost 6 years of taking Actemra the route of administration, frequency of injections, dose of my infusions and frequency of my infusions have all been tweaked. During Covid, Actemra had to be stopped when Actemra was unavailable. I didn't do well when Actemra was stopped. Unlike Prednisone, Actemra can be easily discontinued if necessary. Actemra is like any other medication and it needs to be adjusted based on a person's individual response.

My first experience with Actemra was doing injections every 2 weeks. My rheumatologist wasn't sure what would happen. The reason I was given for starting with injections every 2 weeks was to "play it safe!"

Much of what is known about Actemra is from the research that was done for people with RA. For PMR/GCA what has been learned is mostly based on "good results" from the GIACTA study and not much else.
https://www.nejm.org/doi/full/10.1056/NEJMoa1613849
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When I started with the Actemra injections every two weeks I had to commit to giving Actemra a chance to work. Actemra didn't work immediately and I didn't notice any significant changes at first. I wasn't that sure Actemra was working until I started tapering my Prednisone dose by 1 mg per week. I only tapered my Prednisone dose that quickly "in order to get the inevitable flare over with."

When the flare didn't happen, I decided to tell my rheumatologist that I was down to 3 mg of Prednisone and I wasn't sure what to do next. At least I realized that I was in uncharted territory. My rheumatologist wasn't sure what I should do either until I reminded him that an endocrinologist said I should come back to see her if I ever got down to 3 mg of Prednisone.

My rheumatologist thought it was prudent to check my cortisol level before referring me back to the endocrinologist. When my cortisol level was low, my rheumatologist told me to stop tapering. He told me to stay on 3 mg until I could be evaluated by the endocrinologist.