The various Cathedral 3D Plants by Dr Jacopo are brilliant mods I cannot play without. Though in VR the plants appear overly large. I decided to address this by simply shrinking the plant meshes using NifSkope. 

Plants covered: Deathbell, Lavender, Mountain Flower, Nightshade, Snow Berry, Sword Fern, Thistle, Tundra Cotton, Dead Shrub, Thicket.

BOS Version: The Base Object Swapper version covers all the same plants as the mesh replacer version. It does NOT require the mesh replacer version, in fact, you can only use one main file. If you use the mesh replacer version along with the BOS version you will reduce the plant sizes twice and end up with very small plant meshes in game. 
The BOS version comes preconfigured with the same size edits as the mesh replacer version, but, with the BOS version you are able to edit the plant sizes yourself to suite your specific taste, see the end of the mod description for instructions.

Compatibility:
As this replaces only the mesh files, the original mods are still required for the textures.

Installation:
Mesh Replacer Version comes with a Fomod installer including all replacer options. Use your preferred mod manager to install as per normal. Give my mod priority / let it overwrite the original mods.

BOS Version should have no conflicts.

Credits:
Dr Jacopo (Link to his profile page's "user files" section where all original mods can be found)
NifSkope
Catnyss for their article How to fix meshes yourself 
pytheian for suggesting Catnyss's lighting fix
Subtypes Of Snowberries - Base Object Swapper by wankingSkeever
Plump Cathedral 3D Tundra Cotton and Deathbell by tarlazo

And a special thanks to HamsterSensei12 for inspiring me to make this :)
For the BOS version I also used HasmsterSensei12's mod Size Matters as a base to work from. 


BOS Editing Example:
Open the SmallerCathedral3DPlants_SWAP.ini file and change the numbers in brackets after each plant to the size you would prefer.
                                                                                                                                                                                                                                                                                  

Death Bell, my setting:   

;TreeFloraDeathBell01
0xBB94B~Skyrim.esm|scale(0.75)

This reduces the Death Bell to 75% of its vanilla size.
                                                                                                                                                                                                                                                                                  

If you would prefer to have it at 50% of vanilla size simply change the text, in brackets, as follows:

 ;TreeFloraDeathBell01
0xBB94B~Skyrim.esm|scale(0.5)
                                                                                                                                                                                                                                                                                  

You can also increase the size to be larger than vanilla, say you would like the Death Bell to be twice the size of vanilla, change the text as follows:

 ;TreeFloraDeathBell01
0xBB94B~Skyrim.esm|scale(2.0)