@youngseasoon I had the same big idea as you before and after modding gta v since summer 2016 here is what I've learned.
- Model choice
Whether a model has LOD's or not can reduce textuere loss. For adding a few models in the game, its not a big deal but, as you heavily modify your game, you need to start using more optimized models as replacements. Also don't be afraid to choose a few low poly models with good LOD's if you don't use it that much.
When installing car mods, make sure you install 1 at a time and make backups of all .Meta files you modify. Personally, I export them in openIV and use notepad+ to edit the Meta lines before saving a copy and re-importing back into the game using OpenIV. This helps out a ton especially when there's a problem so you can go back and troubleshoot gta acting up.
Some cars in the wrong slot can create tuning issues (or amusing glitches) You'll also run into a few models that do not have custom tuning for them (the banshee is a great example) . However, with a little thinking outside the box, you can manipulate this to your advantage by modifying the carvariations.meta tuning kits to your liking (something a lot more complex but you'll understand how to do it eventually) .
I also noticed that lower traffic gamconfigs can increase stability slightly.
Also i highly recommend making a table with all the car slots and what works and what does not for organization sake. Personally I have a spreadsheet document with all the cars and, what i've placed in those slots that worked (or failed).
Edit: one last thing use a mods folder in openIV. It will make your life so much easier.