>>10844972
Just choosing the one you like the most might be unsatisfying, because as someone who is also between styles that seems to change day by day for me. Trying to find a meeting point between the three that still appeals to your tastes could be an option. That being said, contrast isn't necessarily bad, it just needs to be carefully thought out. If you really want everything to be matchy though I'd suggest choosing a common color scheme that can still incorporate motifs and details that suit each style (ex. dark color scheme but really girly feeling decor/details). Adjusting how sweet-leaning or how classic/gothic-leaning your room appears would probably depend on the colors or details you choose.
To use myself as an example, my choice of decor is admittedly easy to balance since I'm a sweet & classic lolita and I love pastels & floral motifs in both styles. I have a lot of light colored, sweet-friendly items (like super pink bedding & pillows, stuffed animals, sanrio merchandise/cutesy knickknacks, mostly white furniture) that I like to balance out with more classic-friendly items. My desk, mirror and jewelry box are all dark wood, I have an antique tea cart that I like to display items on and use for storage, a lot of my wall decor is more landscape & flower paintings/vintage postcards, and most of my storage containers can be considered a little more classic than sweet (again, simple, delicate florals on light colored backgrounds on things like boxes, pen containers, etc.)
tl;dr mixing decor themes can be done well, it's really all about doing it carefully and taking into consideration how the items you choose balance each other out. If you're okay with things not being super matchy, cool, but think carefully how your decor interacts with other items you own.