The ban issue becomes crystal clear when you consider the two cases separately. Let's walk through it.
Single-player modding
Mods that affect single-player only (texture swaps, custom maps, MLOs added in SP) have generally not led to bans since the 2017 OpenIV rollback.
Risk: negligible, if you avoid online play entirely.
Online modding
Aggressively enforced. Cheating tools, aimbots, money glitches and modded gameplay in multiplayer sessions can all get you banned.
Risk: high. Keep single-player mods out of your online games.
The grey zone
Some mods change game files in ways that impact both single-player and online behaviour. Best practice is to make sure your modded install never touches online play. Some players have a clean install for online play and a modded install for single-player.