The ability to lock and unlock options depends on the type of event. For both Quickstart and checksites the defaults are set and where it makes sense, the user can change them as desired. Neither of these type of events are expected to be shared (other than a checksite for testing and validation purposes) so you can change things like seeing your location or track before running if you want. Neither of these types of events require you to be an admin. As they are really personal events, locking something does not really make sense.
A regular event is set up by an administrator where the options can be set and locked during setup so all runners are using the same settings (would not be fair for someone to change the punch tolerance to 30m while everyone else was set at 15). How this is handled depends of the specific item - for example, a user cannot change the end date of an event nor can the admin unlock that item for users.
I'm not sure what the issue with the checksites is for you as you do not need to be an admin - just a guess but are you trying to access it from the phone app? The Checksite menu item is only to open a pre-made checksite event, not to make one (the PIN requested is produced when a Checksite is set up). The main web console page https://console.maprun.net/#/ has the "setup Checksite" menu option (you do not need to be logged in as an admin).
No way other than the trust system! Also, keep in mind that there is no consolidated results for Checksites - it's personal only. Moving to the next level requires the admin designation to setup a "real" event, as described in the link I included. If you need more than just this checksite, you might want to contact firstname.lastname@example.org and see what help they can provide. I suspect, for a training session, the checksite will be fine but if you think you will want to use MapRun more often, then getting some experience would be next so you can set up regular events.
Side note - You can set up a Checksite event and then go into the options and set the GPS Watch Mode on, then back and send the event to your watch - run the checksite with MapRunG on your appropriate Garmin watch.
As you mentioned an Event Company, thought I would share this: I was working with an organizer of a 3/8 hour adventure race last fall using MapRun. Wrote a spreadsheet app to register teams and “suck” in map run results, modify as needed and to produce age group results. The more interesting thing was that a large percentage of the 3hr teams had not properly set up MapRun (as per race instructions) - it was a nightmare at the start. There were teams that kept hitting “do not allow access to location services” as they tried to get started! On the other hand, the 8 hr teams took things much more seriously and I think only 1 had any issues - they all came prepared.
Good to hear it worked for those 2 events. I'm only using it for a single stage here, as I don't know that most phones will cope with a 24hr duration. But my event has been the motivation to learn how the app / courses work, so that I can set up a bunch of virtual events in my area.