I hope this is doable. iJammes' Red Dead Trainer lets you set horse values in the *.ini, thereby getting rid of the need for horse-mods.
In addition, it lets you set horse height - again - getting rid of the need for mods. I swapped from this trainer to the Lenny one, as I love the offline mod and want to try RDRFR, as that looks pretty awesome too. In addition, the mod breaks the Red Dead Trainer's camping ability in New Austin, so it was time to clean up in the trainer section ;)
Here is how it looks in the red dead trainer ini:
[Integers & Floats]
Horse : Scale=1.050000
Horse : Run/Sprint Speed=0.000000
[Horse Stats]
Save Horse Stats=True
Bonding Level=4
Speed=7
Acceleration=6
Handling=6
Courage=6
Weight=50
I tried throwing these lst.ini, but no luck
In addition: Disable the Guarma sniper? The areas outside the storyline ones are really nice - and I could disable those in iJamess' trainer as well