Question 1: How do you handle calls from friends/relatives/telemarketers late at night, weekends or vacations? With caller ID, just don't answer if it's inconvenient to you. Let it go to voice mail or let tenants know you prefer text. If there is an actual emergency while you are out of town, you should have a contact with someone you could call to take care of such an issue-friend or handyman. In my experience, I've received more annoying phone calls at 3 am from friends and family than I have from tenants (0 so far).
Question 2: I don't see what the advantage of a PM LLC would be? Many on here will argue against having an LLC for owning properties in and I can't see what a PM LLC would do.
Question 3: I'm a Luddite, so I'm not exactly sure what is being meant here but I have found that when tenants come from online advertisements, I end up with more computer literate tenants than those that respond to a sign in the yard. If you are wanting a more computer literate clientele, go hunting for them where they are. My standard response to technology, modified for this question, is: "How many thousands of years have humans been renting without online work orders?"
Since you're thinking about self managing, honestly, it's not bad. I work my butt off in the beginning to find a good tenant and then after that, most months all I do is take checks to the bank with 11 properties. While I'm not there yet, I can't imagine it would be all that bad at 20 or 25 properties by doubling the calls I get now-very few. I understand the PM fee for finding a tenant as that is a good amount of work but I don't understand paying +/-10% every month to mainly collect rents.