I've used bitdefender as a non-admin user for several years now, never had issues like you describe. In fact, I've only ever got windows prompts and windows firewall prompts for things.
If you're behind a hardware firewall and use the windows firewall + use a non-admin account for day-to-day usage + a reputable AV vendor (see av-test.org rankings), you're basically fine.
If you're super paranoid, grab an extra browser like Opera, enable its VPN, and disable Flash/JavaScript in that one browser. For any risky browsing, use the locked down browser.
For files you're not sure about, throw them in virustotal before downloading. If it's a huge file, just
get the hash output and search that. (This is massively easy with Bash for Windows installed)
ETA
I'm probably not a security expert, but I do work in the industry, have a tech degree, have specialized training, etc. Doesn't mean you should 100% take my word for anything ldo