っぽい: impressions and noticeable tendencies
Separate impressions, a material-like quality, and behavioral tendencies expressed by っぽい. Learn its i-adjective inflection and compare its evaluation with らしい.
An impression rather than an actual identity
この上着は子どもっぽいです。 says that this jacket gives a childlike or childish impression. It does not establish that it is actually classified as children's clothing, and can convey the speaker's evaluation.
安っぽいかばん is a bag that looks cheap or low quality. This differs from 安いかばん, which has a low price, so even an expensive purchase can 安っぽく見える, look cheap.
Qualities and recurring behavior
このスープは水っぽいです。 describes soup as watery or thin. It evaluates the food's consistency rather than classifying it as water itself.
忘れっぽいので、予定をメモしています。 means that the speaker is forgetful and therefore writes down their plans. Here the expression concerns recurring behavior, not appearance, and it does not imply that っぽい can attach to every verb.
Inflection and the comparison with らしい
っぽい inflects like an i-adjective, giving 子どもっぽく見える, 子どもっぽくない, and 子どもっぽかった. It directly modifies a noun in 子どもっぽい服.
子どもらしい笑顔 can positively describe an innocent smile typical of a child. 子どもっぽい態度 can criticize childish behavior, but the actual evaluation depends on the preceding word and the scene.
Quick check: Does 高かったのに、安っぽく見えます。 contradict itself about the price?
Show the answer and why
No. It says that the item was expensive but looks cheap. 安っぽい describes the impression here, not the actual price.