Accordingly, can WiFi owner see what apps I visit?
Yes they can. And not just admins, but potentially anyone on the network could monitor what you access. They can also harvest login information. I've seen people keep open WiFi networks just for the purpose of spying on people who access it.
Subsequently, question is, can my employer see what websites I visit on WiFi? If you're using a company computer (or wifi connection), your employer can not only monitor your work email and projects, but they can log your key strokes, including on “private” sites like Facebook or your personal email account.
Also asked, can WiFi provider see your history incognito?
Unfortunately, private browsing mode won't help you there, contrary to what many internet users think. While incognito mode doesn't store your browsing history, temporary files, or cookies from session to session, it can't shield you from everything. Your internet service provider (ISP) can see your activity.
Can school WiFi see your texts?
If you have connected to school's WiFi, there is not even a single chance that the school takes away your text messages from you, unless the WiFi itself has been hacked by someone other than your school.