I agree that you can have no real control over how someone behaves when they are outside your home, but having a long-term guest, rather than lots of different people in and out, makes sense to me.
Firstly, they are not travellers (at least not the ones that have been contacting me lately, who have mostly been locals in search of a temporary home) and have not been jumping on and off planes and trains etc. or coming from places where you discover a couple of days later there is another COVID-19 peak.
Secondly, there is less vetting to do because you have to do it less often, but can be inquisitive. Long-term guests tend to have more questions and be more open to being asked questions. There is usually much more dialogue so you get a better sense of who they are and their lifestyle. The latter often currently involves working or studying from home so, yes, they may still be out and about in their free time, but that's generally less out and about that people coming for short trips, tourism, meetings etc. who will be using public transport a lot more. My current guest is at home all day during the week and then walks or cycles when he does go out.
I can't say I feel 100% comfortable 100% of the time, but I think for me this is the safest way to continue hosting and I can't really afford not to. I usually have three, rather than one, rooms booked year round and also lost most of my self-employed income due to COVID-19, so having that little bit coming in from renting out a room makes a big difference, especially having had an empty house for months.
In terms of safety measures in the home, my current guest and I barely see each other (sometimes not for days) and when we do, it's a quick chat at a distance. I am lucky though that the house is quite large with enough showers so we don't have to share and communal spaces like the kitchen and entrance hall are also spacious so we're never in close proximity. The house is kept as clean and hygienic as possible, but that's nothing new. The main differences are that I've changed some products, there is constant handwashing and, yes, having to disinfect stuff like door handles and light switches, but I'm not finding it that much more work than normal. I've always been a bit OCD about cleaning counters etc.