The "blurry pixelated big UI" is actually the correct one I believe. The one that you find correct is smaller than what the UI used to be in original The Sims. The "incorrect" one is what it used to be in the vanilla game.
I agree though that the UI is pixelated and messy looking. I don't reallly understand why EA didn't fix the buttons to show correctly on higher resolutions. Half of the buttons in the game have wrong background now so it looks jarring. I also hoped they'd upscale neighbourhood/expansion lots screens so they'd take entire screen space instead of having the black border around everything. It's honestly quite disappointing esp. since the guy behind FreeSO somehow managed to make The Sims Online UI work great on widescreen monitors AND improved graphics greatly while at it. It can be done, it just requires care from the developers.
Also I don't quite understand the reasoning behind using TS1 Complete Collection's rather ugly loading screen instead of the original one from the base game but I guess that's more of a taste question.
