Custom Build for TS4 - What are the best specs for maximum performance?

I would really appreciate some advice from those with computer knowledge!

I am currently playing The Sims 4 on a MacBook Pro from 2010, i have a few expansion packs. My game is set to the lowest graphic settings, it is slow, choppy, and can be laggy at times - I pretty much stopped playing because it’s just not an enjoyable experience. I have been playing The Sims since 2000, but always played on family computers with a mediocre experience.

It has been a dream of mine for years to have a PC/Desktop that runs TS with optimal performance. I want to be able to play the game with all expansion packs, game MODs, ultra graphic settings, fast and smooth panning, and no lagging. I’m considering a custom build because I am anticipating the release of The Sims 5 in the future, and I want to ensure that I can run this future (currently unannounced) game at maximum performance as well. I would prefer not to have to upgrade when the time comes, but custom build would allow the option if needed.

Essentially, I want this build to be the best it can be for the current game, while taking the future into consideration - I would rather it be overkill. Without budget constraints, what specs would you recommend?

Thank you in advance!