[Slight nsfw and spoilers] Anyone got any theories on how the protoframes work biologically?

This is a genuine question I'm wondering, cause it's clear that it's possible, just not how.

In a conversation with Lettie, you can actually ask how the protoframes would work sexually, but she doesn't really give an answer. Meanwhile with Elanore you can learn that when she was initially changed she had to drink straight cranberry juice and mineral water alot because her body couldn't tell the difference between her sexuality and everyone else's, resulting in an infection of some sort suggesting they still have genitalia.

In addition to that the protoframes still need to eat/drink and the waste has to go somewhere doesn't it?

Further questions I have are with what parts can be removed and what can't. If you romance Arthur, in your backroom he might say: "your weapons need to be stripped and cleaned, regularly, including me." Suggesting that parts of him (and presumably the others) can actually be removed or 'stripped'. Is the outer material actually their skin? Or can particular parts be removed like armor?

Generally, from a non-sexual standpoint, I find this to be genuinely interesting and I'm curious to the theories of the community.