Tekken 4 Reborn by TheI3arracuda
Return to the mood, look and feel of Tekken 4 with the Tekken 4 Reborn mod for PC Tekken 7. According to the author, this modding project took around 350 hours to complete and features an overhaul to the game's graphic and sound effects to match those of Tekken 4. The mod is purely audio/visual so I'm pretty sure that this is safe and won't cause any issues when it comes to online match desyncing too. Check out TheI3arracuda's DeviantArt page for the mod to find more details and a download link:
Tekken 4 Reborn ≫ https://www.deviantart.com/thei3arracuda/art/Tekken-4-Reborn-827158950