1. Get a VPN and set it to "always on VPN" and if really having issues "block connections without a VPN". Only then can you keep your wifi on autoconnect. The really good ones are paid, have adblocking and will turn on whether you are connected to wifi or data.
2. Settings, the 3 dots in upper right hand corner, advanced, WIFI control history, see what is controlling your wifi. Tap on each individual one and turn it on or off.
3. Settings, data usage, data saver, tap on, then allowed to use data while data saver is on. Restrict what you do not want accessing your data.
4. Use a 3rd party security app, example Bitdefender, malwarebytes, Sophos, Comodo or something with a track record of being reliable. Google Playstore is notorious for letting sketchy virus ridden apps through. Turn off play protect and protect the apps on your devices or your devices from the apps.
5. Settings, apps, 3 dots in upper right corner, permissions manager. Go down the list, click on each category and each apps cripple everything you don't want accessing certain content on your devices.
6. Settings, apps, 3 dots upper right corner, special access. Number one, change system settings, go down the list, touch each entry to turn it on or off. If it is not a needed system app the you can turn it off. Next usage data same process. Allowed to use data when data saver is on, restrict whatever you can will save battery life. Device admin, find my mobile should be off. Samsung has one in your Samsung apps this is the Google one. Very few things should be allowed admin, for example I have only one Samsung Pay. Wifi control, cripple as much as you can, will save battery. Use premium text message services, same process.
7. Settings accessibility, installed services Turn off what you absolutely do not want.
8. If you are having security issues--step 1 take out the sim card, disconnect from wifi and if you can't, unplug your router. Save your content by doing a smartswitch, on an external hard drive or microSD card. Then factory data reset. Afterwards transfer your content back using smartswitch.
9. Snapshot or screen save this list. For me this is the short list but should get you started in controlling your devices.
10. Alternative browsers, you can use more than one. Brave, iron, Ghostery, DuckDuckGo, and Tenta. These do not track have search, and built-in VPNs.VPN. I normally use 5 and keep my tabs open because of no tracking. Also, use the Samsung browser for certain content.