I personally know how speed differential can make people fear for their safety and spoil their experience. There's no real common etiquette out there for this scenario in my parts, so I opt to slow down and look for body language and other indicators. It's like "traffic free space", except I can use a bell to force a reaction.
I'd prefer if there were some signs posted displaying etiquette, like on ski slopes, where the faster more skilled person is held accountable to avoid hitting the people they're passing. Similar to etiquette where you leave the left side of escalators open for passers, or leave lanes open on the road for faster traffic. In the US, we have "yield" system, but others interpret it as a "stop and get off the trail" sign, rather than a typical road's yield sign where you can go as long as there's room.
One exception to the rule: I'll slow down enough to get a better look if there's unpredictable pets or kids, or if I hear a gasp of shock or whatever, or if the people look like they might need outside attention.
I'm forever passing clockwork bikes on my way home each day, at least 20-25 a day (nobody has overtaken me yet....) I treat it like I would if I was driving a car and passing any bike. Slow down if needed, give a wide berth, don't be doing 30KPH, that's enough surely?
Now dogs and tiny people, they scare me. Unpredictable, tiny and come out of nowhere.
Ha yes felt the same on my first ride at our local trail centre , I left the bike in the van until I was ready to go and tried not to leave close to other riders . I only passed one rider but held back and changed to eco to pass him so I was working hard , I felt like a big of a fraud to be honest . I guess the feeling will go