Base Goten and Trunks (Pre) vs. Piccolo

I kind of agree with CoH in that Boo's appearance is probably based on whoever absorbed is affecting him the most. But in an overwhelmingly large majority of cases, this will just be a matter of who inside him is strongest and thus adding the most power.

The Grand Kaioshin is the only known exception to that trend. But not Piccolo. If being smarter were all it took, then Boo would still resemble him after absorbing Gohan, too!

Yeah, keep in mind that as per the rules of the tournament, Eighteen would be disqualified if she killed her opponent, and thus not get her precious prize money. It'd make sense for her to be pulling her punches somewhat while trying to gauge how powerful "Mighty Mask" was.

Not to mention that she is acting totally nonchalant and not stressed in the slightest during the battle, whereas Goten and Trunks are clearly struggling; not an indication of an "even battle." Even after going Super Saiyan, they still think they're at a disadvantage, but if they were already truly on-par with her in base, then once they're now 50x stronger than her there's no way the suit would matter at all.

I'd consider 18 to measure up to the kids about the same as Piccolo compares to the adult Saiyans; smack dab right in-between their base and full Super Saiyan power.

Uh... That said, to be on-topic, the base kids don't stand a chance against Piccolo. Though after their stint in the Room of Spirit and Time, they'd be able to put up a good fight working together... as Super Saiyans.

Come to think of it, I don't see anything wrong with Piccolo "rivaling" Gohan as well. Gohan had lost so much power that Vegeta was pretty much ashamed of him. One could have the kids below Piccolo but still powerful enough to greatly impress Gohan. But I wouldn't go so far as to say one "has to" have anything of the sort or otherwise.

It's just that we have no evidence to presume they did reach Super Saiyan 2 (as individuals outside of Fusion anyway). It's certainly possible.

It's likewise entirely possible or even likely that Chi Chi made pancakes for breakfast in the morning before she, Goten, and Gohan left for the Tournament, and that Piccolo visited on his own way there so she squeezed some fresh orange juice for him. But we have zero evidence or indication that she actually did.