If you have the budget, I highly recommend moving your compensation points up and focusing on top engineers in remote locations. It's much easier to vet people who have an established online track record and you can tap references from well-known companies. Unfortunately this way you will miss out on some great candidates that haven't yet established themselves, so you still have to branch out.
For remote work we require video interviews and cameras on during meetings. We'd make an exception if someone really needed accommodations to keep their camera off for some reason, but otherwise it's cameras on. I know some people don't like this, but it improves communication and team cohesion in a noticeable way. It also immediately highlights fraud like this.
Get your security team involved. You should be tracking where remote employees access your VPN and company services. Don't be afraid to ask about discrepancies and changes. If someone has logged in from one IP or region for the first 4 weeks and then suddenly you're seeing new logins from a different city or country, investigate. I don't care if people travel, but we need to firmly understand the security situation.
Watch out for people with frequent excuses for missing meetings, having to turn their camera off, excuses like "my camera isn't working today", and so on. Send everyone known-good webcams and company laptops.
And as always, performance management is key. Managing remote is harder than managing in person, and I say that as someone who manages remote and loves remote teams. You need strong performance management practices in place and clear ways to measure it. People who aren't getting their work done should show up quickly in your system and warrant additional manager investigation.
But if someone shows up in Zoom who isn't the person you hired, lock it down ASAP. Don't let being "nice" get in the way of handling an urgent security situation. Someone you didn't hire who hasn't agreed to your contracts is in your system, and that's a red alert emergency.