Looking to add a 3rd card to my Platinum/Gold combo

I have an Amex Platinum and Gold and looking to add a 3rd card for a few reasons. Main reason is to have a card that's accepted in more places. But also to fill in the missing categories to maximize during my day to day use. My daily driver is my AMEX gold. I really only use my Platinum when I travel and as a coupon book. I was considering the Venture X or the Chase Sapphire Reserve as a more balanced card. So as you can see it doesn't have to be in the same ecosystem, but it's important that transfer partners overlap. I don't care if I have to pay a high annual fee.

I'm currently leaning towards Chasse Sapphire Reserve, but I keep going back and forth between that and Venture X. I want ease of use when using my points and flexibility with perks.