I am holding hope that Rimnoa has more going on with him than just someone whose purpose is to try and one-up Washio and predictably get one-upped in turn. He is someone Washio considers a friend enough to try and stay the night at his house, and Rimnoa did try and let him stay in his balcony which he even took time and care to decorate so to make it more livable for Washio.
This. I'm more frustrated with the lack of clear characterization they have given Rimnoa beyond "prick elf" especially after they've shown some hidden depths with his attitude towards Washio in certain circumstances (like the scenario you mentioned with him offering to let Washio stay despite protesting).
I was hoping that he was just going to end up being Tsundere and actually wants Washio's respect which is why he puts on airs so much and goes about preening to such a high degree. Either that or he knows Washio's past and is purposefully downplaying him to help Washio stay lowkey instead of everyone finding out he was a hero previously.
Again, we see Washio has some trauma he is either trying to move past or struggling to cope with involving the monster girls and "high society" as it were. The author has overplayed the "secret past" card way too much and needs to start giving some more solid and tangible answers to why Washio is the way he is. The tease only gets you so far, you can't just keep baiting people and never deliver and it's beyond the point of a hook reeling new readers in.
I'm fine with Rimnoa being a prick and I'm fine with Washio being a pushover who lets people think he's a washed up failure as long as it leads to something interesting down the line. I've given the story the benefit of doubt numerous times already but even my patience is wearing thin.