#1
Well, I tried something, first look at this: :) - YouTube
As you can see I used SetLocalPlayerAsGhost(PlayerPedId(), true) also I tried SetNetworkVehicleAsGhost(GetVehiclePedIsIn(PlayerPedId()), true) and both work but… I can’t find a native to disable it. False or 0 don’t work for me sadly. I wonder if there is even a way to disable it…
FreezeEntityPosition also works for me but ghost mode is preferable ofc as I want to avoid players bump each other during time trials not only during the countdown.
#2
I use this awesome script (SimplePassive: Passive Mode in your FiveM server, just like in GTA:O) for passive mode whenever a player wants it on. The main problem of this script is the auto-adjustment of the camera when you go through another player in passive mode. It’s like the camera has collision with other entities. DisableCamCollisionForObject(or ForEntity as there are 2 natives) doesn’t work 
Sorce code -
Lines that have been edited by me: 171, 222, 250, 265