I'm obviously not qualified to comment directly, but I'd be wary of assuming that there is, necessarily, one single and definitive radical feminist position on this (these) issue(s).
Do you have to know what the radical feminist position on this is before you can reach your own position?
To expand on my previous post now that I'm on a computer rather than a phone, it seems that one aspect of why some women might characterise the 'transgender movement' as being an attack on female identity specifically is that part of that movement is composed of people who were born and still are biologically male and were socialised as men (with all the implications behind that), insisting that they be viewed and treated as women in absolutely every respect, including being admitted to often hard-fought for women/female only spaces where they feel safe.
As a man, I don't feel the need for such spaces, so the idea of people who were born and may still be biologically female and were socialised as women being admitted to men/male only spaces (whatever they are, exactly) is frankly not one that bothers me in the slightest.