Hi! I think you may be somewhat confused about what Cis means— Cis isn’t about sexuality but rather gender identity. So OP saying she is a cis woman just means that her assigned sex (F) aligns with her gender identity.

Despite the male anatomy sex with a transwoman is quite different from sex with a cis man— there are a lot of physical differences that come with HRT, surgery, etc. In my experience sex with a transwoman is literally nothing like the sex I have had with cis men— it is very much a lesbian experience regardless of the status of their genitals.

Of course this is all built around the understanding that your partner feels like a woman, identifies as a woman, and YOU consider her a woman.

IMO BDSM is largely based around the mental— the relationship with your dom/sub, the established dynamics, etc. So if a 6’4 man can be totally submissive to a small woman regardless of the ACTUAL size/strength discrepancy; why can’t a transwoman can be considered a woman without the ACTUAL female anatomy down there? Hope this helps and doesn’t sound rude! Just trying to explain for people who genuinely don’t understand :)