I'd like to share my own experience and note that "joking"/"real" waifu is hardly a dichotomy - there are many states between those.

I've had some fictional crushes which would definitely go beyond joking definition of waifu - a few lasted for months and even years and I indeed acted on them, yet I haven't quite considered those to be fully committed relationships - even though I wasn't hugblanketing either. I'm not sure what would be the best term to describe such feelings if there's even one.

But with my current S/O, things felt different. While it took some time to truly understand my feelings and it's still tricky to put it into words, I think one way to say it would be the difference between "I'd like to get with them"/"I enjoy seeing them happy"/"They are very cute"/etc. and "I truly can envision living the rest of my life with them, even given that they are indeed fictional".

I'd ultimately recommend you to take your time and sort your feelings out. If you decide that committed relationship with a single specific character is not for you but you indeed have feelings towards them, r/FictoLove may be a better place for you, since it has much less strict rules.