In my experience with FiveM at least, all mods are server side, and streamed to the clients. You need to contact the server owners to find out what is installed

https://forums.gta5-mods.com/topic/14021/mod-approval-thread/4

data protection and copyright are two different things, neither of which apply to your situation. According to the EULA any and all assets created and used in game become property of Rockstar anyway, including all mods.

As a general rule, if the mod says you're okay to use it in FiveM, you can use it on your server. If it says you can't, then don't, and if it doesn't specify or you're unsure, message the creator and ask permission.

That occurs when you don't use ENB. Everyone that uses Quant without ENB will experience this.

Red dots on the minimap is an enemy, thats a normal part of gameplay. With regards to cars disappearing, the game will naturally despawn vehicles once they are out of range to reduce memory load. You need a vehicle persistence mod if you plan to leave cars around the map to return to later.

Yeah textures don't affect frames at all noticeably, you can leave them on max. Yeah one streamer I watch gets 120fps from a gtx3090 with graphics aaalll the way down. The game was designed with 30fps console play in mind, 60fps is a good result imo

I went from 8GB to 32GB, didn't affect my frames but did reduce the frequency of memory related crashes. I'm only on an old 1050ti with a 2500k i5. The GPU is the standard throttle point for fps here. Shadows and lighting are the usual hogs for GPU usage, of which ENB ramps up the quality of both. If you're still struggling with ENB and Reshade off then try turning down the shadow quality in the GTA settings menu. 100+ fps for GTA is only really possible on top spec machines with the graphics settings turned right down (look at some of the speedrunner setups for an idea)

As soon as I saw ENB and Reshade that said it all.

ENB alone will tank your frames. De-activate it and watch your fps skyrocket. On max graphics my machine will sit at around 30fps and plummet to 12 with ENB enabled.

the liveries need to be created as a separate model with an emmissive texture in zmodeller, this is not something that can be done with liveries alone

if you look in the vehicles.meta you will see that it borrows handling from one of the SUVs (I forget which one) and the centre of mass is all out of whack, especially if you are using Eddlms handling overhaul. You can add your own handling.meta and add it to the content.xml file, look at other mods with custom handling to see how it is done.