JoinUs VS objects

The complete list of custom content that is included with OpenRCT2 can be found here

There's no way to place a saved track design if you don't have at least one vehicle type that uses that track. There is a pending PR to have a hybrid and single rail train included with OpenRCT2 but for now they must be downloaded separately.

I haven’t built one personally, but I believe the track is in OpenRCT2 by default using the arbitrary rides option in the cheat menu. You’ll have to download the raptor train separately, though, here: https://github.com/OpenRCT2/objects/pull/135

This is an OpenRCT2 official object so it should be included with OpenRCT2 - maybe your JSON objects are out of date or it got deleted somehow? You can find all the OpenRCT2 objects here.

There are a few things still being worked on – different path styles and missing train types come to mind – but it's largely a 1:1 experience with playing the RCT1 scenarios in OpenRCT2. Certainly better than playing them in RCT Classic, which hasn't implemented the terrain types unique to RCT1. The only reason I'd advocate playing RCT1 in its original form over OpenRCT2 is if you wanted to play within the limitations of RCT1, like not being able to raise objects and not having RCT2's default scenery selection. RCT1 is also easier to get running than RCT2 on modern Windows, since you can hack it to run 1080p and you can remove the need for physical discs if you don't have the GOG version.

No, the single rail trains still haven't been merged

IIRC, it's technically implemented already - the "No Entrance" option is implemented as a custom object - however, without the new save format, the list of available station types must be hardcoded.

You mean the RMC Raptor? Yes, spacek531 is: https://github.com/OpenRCT2/objects/pull/135

Note that although the train (which was made /u/spacek_toast) is planned to be included also, at this moment in time it hasn't been merged, so for now you will have to download that separately in order to use it. As with the hybrid coaster, if you don't have any train type installed you can still build the track using the arbitrary ride type cheat, but really there's no vanilla train that works, so I recommend downloading the custom one.