My c!Tubbo is a ram and his horns grow in an arc: first up and back, then around and out. They're functional for fighting by the time he's around 16, and you would be hard pressed to deal any sort of head trauma to this guy. The horns grow continually without shedding, though growth slows down significantly once Tubbo reaches maturity. The tissue inside the keratin sheath is live and will bleed if insulted.
c!Ranboo has enderman horns, which are designed to deal piercing damage and aren't particularly functional in combat. In enderman society horn size denotes prestige in both age and magic power, and some elder endermen can have truly massive horns. Ranboo, being only half enderman and not having the same range of powers, will never see this level of growth. Just like Tubbo, the tissue inside his horns is live.
Misc Headcanons:
Tubbo's ears were floppy until he was around 14
Ranboo can unhinge his jaw, but usually only does so when he feels severely threatened
Tubbo is naturally very fluffy. Lots of fur. A pain to clean but delightful for spouse snuggles
Both Tubbo and Ranboo need regular hoof trims, and they do it for each other because it's easier + bonding time
Tubbo is extremely sure-footed and can walk unimpeded on almost any terrain
Ranboo looks a little like a chihuahua with teary eyes due to the water burns and it gives him a terribly pathetic vibe
The firework explosion took out Tubbo's right eye and disfigured the right side of his face. The scars cause pulling unless they are regularly medicated, and are sensitive to sunlight (this is part of the reason he wears his bangs so long). The less severe wounds fade over time.
Ranboo's development is as follows: Sickly Victorian Child -> Normal Young Man With No Issues At All No Sir -> Milf. I will not rescind my statement
Tubbo has an incredible sense of smell
Ranboo is prone to illness from stress, and this sometimes manifests as hoof infections in the corium and digital cushion
Dono: Rest in peace QSMP, you would've loved pride month.
Phil: PFTT— [Laughs] Dude, it was Pride Month every day on that server, what are you talking about? Every single day on that server was just Pride. Realistically, QSMP was just an excuse for Quackity just to flirt with men. Let's be honest. I mean– [Laughs] The true- the true reason. The true reason was Big Q wanted to flirt with men. [...] It was a lot of fun though. I really enjoyed it. [Laughs] The gay roleplay went so hard, it was really funny.
It actually warms my heart to see Cellbit so comfortable showing his pride in being Ace. I know it was a terrible way he had to come out but I’m so so happy to see the widespread acceptance and outpouring of love for him from the community. HAPPY PRIDE TO ALL MY FELLOW ACES! 🖤🩶🤍💜