Depends on the MC and the Story/Setup... if its a Shota family thing, its small. If MC is an Adult, a normal one does the job perfectly fine... when it comes to Futa stuff, i prefer them dellusional Monster Cocks and Ahegao facec tbh.
I guess except for Futa stuff, it should be just realistic.
I also think that there should be more Variation in games like in "Daily live in Countryside" where you can make it small to access some scenes.
Would definitely just prefer it to be in a medium area. but ig that also depends on the MC or even the other males in the game i suppose. like if it makes sense for them